Truth suffers from too much analysis

David Hume on Modern Science

Posted by allzermalmer on June 4, 2011

This blog will be taking some of the British Empiricists David Hume’s doctrine, and seeing how modern science would be judged from such a doctrine. David Hume’s place is that of an empiricist, which means that he says that knowledge of matters of fact are to be comes from the senses. From this stand point, we can see how modern science would be judged from an empiricist position.

I will be using some of his stated position from Treatise of Human Nature and Enquiry Concerning Human Understanding.

Hume starts out the Treatise of Human Nature (ToHN) by presenting his Fork, or Hume’s Fork. This divides knowledge into two different sorts. He also presents it in his An Enquiry Concerning Human Understanding (ECHU). They are both, respectively, as follows.

“All the perceptions of the human mind resolve themselves into two distinct kinds, which I shall call Impressions and Ideas.” (ToHN)

“Here therefore we may divide all the perceptions of the mind into two classes or species, which are distinguished by their different degrees of force and vivacity. The less forcible and lively are commonly denominated Thoughts or Ideas.The other species want a name in our language, and in most others; I suppose, because it was not requisite for any, but philosophical purposes, to rank them under a general term or appellation. Let us, therefore, use a little freedom, and call them Impressions; employing that word in a sense somewhat different from the usual. By the term impression, then, I mean all our more lively perceptions, when we hear, or see, or feel, or love, or hate, or desire, or will. And impressions are distinguished from ideas, which are the less lively perceptions, of which we are conscious, when we reflect on any of those sensations or movements above mentioned.” (ECHU)

Hume goes on to state, in short, that sensations are impressions. These would count as our senses of sight, touch, taste, smell and sound. These are our contact with the world, or what we can only know of the world. It is the most immediate thing that is present to our consciousness. It is what informs us. Ideas are those of thought, which is like me sitting here and wondering, “I wonder what Shaquille O’Neal is going to do now that he retired from the NBA”.

The difference between them are the force that they come to my consciousness. The sensation of touch is not as lively as my hands touch the keyboard as the thoughts I have, like the example that I gave. I can ignore my thoughts, but I cannot ignore my senses.

Hume, in the Treatise, goes on to break down Impressions and Ideas into simple and complex.

“Simple perceptions or impressions and ideas are such as admit of no distinction nor separation. The complex are the contrary to these, and may be distinguished into parts.” (ToHN)

A simple impression would be that of a color, like, say, the color red. A complex impression would be something like, say, an apple. A complex impression can be broken down into simple impressions, but a simple impression cannot be broken down. Thus, we find that simple impressions are like bricks, and these bricks are joined to form a house. The house is complex, yet the bricks are not complex.

This distinction between simple and complex also hold with ideas. Thus, I have the simple idea of red. I also have the complex idea of an apple. This idea of an apple has simple ideas like, red, sweet, hard, and round. Yet each of these things just listed are simple ideas.

In order to get a better idea of this, we can go to the original source of such an idea that Hume comes up with, which comes from George Berkeley. This comes from George Berkeley’s A Treatise Concerning the Principles of Human Knowledge.

“By sight I have the ideas of light and colours, with their several degrees and variations. By touch I perceive hard and soft, heat and cold, motion and resistance, and of all these more and less either as to quantity or degree. Smelling furnishes me with odours; the palate with tastes; and hearing conveys sounds to the mind in all their variety of tone and composition. And as several of these are observed to accompany each other, they come to be marked by one name, and so to be reputed as one thing. Thus, for example a certain colour, taste, smell, figure and consistence having been observed to go together, are accounted one distinct thing, signified by the name apple Other collections of ideas constitute a stone, a tree, a book, and the like sensible things–which as they are pleasing or disagreeable excite the passions of love, hatred, joy, grief, and so forth.” (TCPHK)

Hume goes on to tell us, through his empiricist epistemology, that impressions go ahead ideas. He also goes on to say that, generally, ideas are derived from impressions. I cannot have the idea of green without first having the impression of green. Thus, we find there is an asymmetrical relationship. Every simple  idea has a correspondence with a simple impression. But he does go on to say that many complex ideas don’t correspond with complex impressions. I can have the complex idea of a city of gold and diamonds, yet I do not have a complex impression of a city of gold and diamonds. I form such an idea through my imagination. I do this by combining simple ideas, which are copies of simple impressions, into a complex idea that I have not experienced myself.

Hume also goes on to bring about a major distinction, which is related to that of ideas and impressions. This is his Matter of Fact and Relation of Ideas. This is related to Leibinz’s distinction of Truth of Fact and Truth of Ideas. This has been a major distinction in epistemology ever since it was brought about, and took a major critic by W.V. Quine in his Two Dogmas of Empiricism.

“All the objects of human reason or enquiry may naturally be divided into two kinds, to wit, Relations of Ideas, and Matters of Fact.

Of the first kind are the sciences of Geometry, Algebra, and Arithmetic; and in short, every affirmation which is either intuitively or demonstratively certain. That the square of the hypothenuse is equal to the square of the two sides, is a proposition which expresses a relation between these figures. That three times five is equal to the half of thirty, expresses a relation between these numbers. Propositions of this kind are discoverable by the mere operation of thought, without dependence on what is anywhere existent in the universe. Though there never were a circle or triangle in nature, the truths demonstrated by Euclid would for ever retain their certainty and evidence.

Matters of fact, which are the second objects of human reason, are not ascertained in the same manner; nor is our evidence of their truth, however great, of a like nature with the foregoing. The contrary of every matter of fact is still possible; because it can never imply a contradiction, and is conceived by the mind with the same facility and distinctness, as if ever so conformable to reality. That the sun will not rise to-morrow is no less intelligible a proposition, and implies no more contradiction than the affirmation, that it will rise. We should in vain, therefore, attempt to demonstrate its falsehood. Were it demonstratively false, it would imply a contradiction, and could never be distinctly conceived by the mind.” (ECHU)

So a matter of fact would be something like this, “The white crow ate a white squirrel”. A relation of idea would be something like this, “All bachelors are unmarried males”. The easiest way to understand this is based on the contradiction. A relation of idea is a statement that would be contradictory to deny. A matter of fact is a statement that there’s no contradiction in denying it. Thus, I could deny “The white crow ate a white squirrel”. However, I cannot deny that “all bachelors are unmarried males” without forming a contradiction. This is the difference between contingent statements and tautological statements.

A contingent statement is a statement that, when you check their truth table, it is true in at least one row of the truth table. A tautological statement is a statement that, when you check their truth table, it is true in every row of the truth table. Thus, the difference is contingent/not self-contradictory to deny and tautology/self-contradictory to deny.

The other major difference is that one is based on the senses and the other is based on thoughts alone. Thus, a relation of idea is true based on the words that one uses and is not based on the senses. Mathematics and Logic are based on relation of ideas.

Hume goes on to show that matters of fact are based on causality, and that this holds between our sensations. He also goes on to state that it is based on induction. Hume is known, or infamous, for his critique on causality and induction. He basically said that we never experience causality in our sensations, and that induction begs the question and relies on an assumption that is not given in experience. This would lead one to think that this dissolves the matter of fact. This would be true if Hume did not invoke a psychological stance known as Custom of Habit. We notice one thing follow another (causality), and we notice this many time (induction), that we come to say that one is caused by the other.

Take the example of fire and smoke. I start a fire (A) and I see smoke (B). Hume tells us that we see two different things. Start fire. See smoke. We find that fire is followed by smoke. This means nothing by itself if we only experience it once. However, when we experience it many times, then we come to combine them together through custom of habit. Now, when I see a fire, I come to expect to see smoke. If I see smoke, then I conclude that there is a fire. This is something that is not found in the senses. It is something that the mind imposes onto the sensations. Hume also calls this Constant Conjunction.

There is a simple logical inference that works just like this. This inference is called Conjunction. The symbolic form follows like thus: (1.) A, (2.) B; (C.) A&B.The inference follows like thus in sentences: (1.) See fire, (2.) See smoke; (C.) See fire and See smoke. We see these things so often in experience that we make this conjunction constantly. Thus, it is a constant conjunction. And another side note, we combine these two single  events and can put them in a conditional statement of, If see fire then see smoke. We combine these two separate events and form a causal line or reasoning when we notice it more often through experience.

Science is an empirical philosophy. It is based on an empirical epistemology, and an empiricist epistemology is a sub-class of an empirical epistemology. An empirical epistemology states, “all true knowledge must, at some point, be associated with empirical correspondences and consequences.” (George Gale). Also, “Scientific knowledge, at some point in its construction, must be securely tied into the human sensory system. If it were impossible in principle that some proposed scientific object could ever, under any circumstance, leave a sensible trace in a human sensory system, then that object, no matter what its potential as an explanatory or theoretical entity, could not be considered as a candidate of scientific existence.” (George Gale)

Science will collect all sorts of sensory information, and categorize it to make it easier to understand and use. Thus, we can come across a white swan and investigate it and learn new things. We will collect this information and put it under the class of a swan, and then put some of the other information under as a sub-class of a swan. Like they are sexual creatures, lay eggs, and eat certain creatures.We will find categorical statements like, “Swans lay eggs”, “Swans have wings”, “Swans having mating rituals”, and etc.

One of the most important things of science is prediction. It is actually one of the most important things, if not the most important. It will predict what we shall observe with our senses. This is known as testability. In order to be a scientific hypothesis, the hypothesis must make predictions of what we shall observe with our senses. For example, a girl who is a friend of mine could come up to me with something that is on her mind. She could say, “I think my boyfriend is cheating on me.” I could come up with a hypothesis to help her with this problem, and maybe solve it. I could say, “If your boyfriend is cheating on you, then you will smell perfume on his clothes when he comes back from a late night out on the town.” The consequence of my hypothesis is testable. She can smell him when he comes back from a late night out on the town.

Now science creates hypothesis. So what are hypothesis? “A hypothesis is a tentative statement, subject to investigation, that is advanced to explain an event or relate facts in a given context….Hypothetical reasoning is the process of inferring certain implications from a hypothesis and then making observations or conducting experiments to decide whether these implications are true.” (Logic: An Introduction). Science comes up with hypothesis that collect all of our observations together, and helps make predictions. They are general in character, and can be applied almost universally into anything that meets those same conditions.

These hypothesis can be based either on deduction or based on induction. “All of the sciences, and especially the quantitative ones, rely heavily on the reliability of logical reasoning and deductively valid arguments; the sciences also rely on inductive arguments-ones which move from finite bodies of data to general theories.” (Philosophy of Science)

Induction is about reasoning from what is observed to what is as yet unobserved but can be observed. From example, I have made many observations of black crows. I go on to make a prediction of the next crow that I observe shall be black. Now, I am not currently seeing a crow, which means it is unobserved. However, I can, in principle, observe it at a future date. It is known as inductive enumeration to move from past observations to a general conclusion. Its reasoning follows this typical form:
(1.) Black crow
(2.) Black crow
(3.) Black crow

(C.) All crows are black

There is also statistical induction, which just moves from past observations to stating the statistical probability of the conclusion. In past observations I have found that I have gotten heads 50% of the time when I flipped it. Thus, I predict that there is a 50% chance I will get heads when I flip a coin.

Now what I have gone through is a just a rough outline of science, but it does cover some of the big points of science. But there are two things that I did leave out. (1.) Science likes to use causal reasoning to explain things, and (2.) Science invokes many unobservables to explain our experiences. (1.) and (2.) are related closely, but they are not exactly the same.

I can causally explain that I hear a loud sound because a gun went off. I could observe a gun being fired and hear the sound from the gun, and say the sound I heard based on the gun being fired. However, I cannot observe atoms but I can observe what the atoms supposedly caused, like streaks in a cloud chamber.

Now we cannot use inductive arguments to move from observed to what can never be observed with the senses. For example, I cannot move from what I experience with my senses to make the inductive generalization or inductive argument, to something that I can never observe with my senses. Thus, induction only works from what is observed to what can be observed. So how do we come up with hypothesis that deal with what is unobserved? We use deductive arguments.

Deductive arguments carry the form of a conditional statement. A conditional statement carries this form: X→Y. [As a side note, logically, we can turn an inductive conclusion into a conditional statement: All X is Y↔ (X→Y)]. The antecedent of the conditional statement, X, is based on something that is unobservable. Its something that we can never experience with our senses. However, through much logical reasoning, we deduce an observable consequent (something we can observe with our senses), which is Y. Thus, science starts out with induction, and then eventually moves to deduction.

Now, we have already gone over the problem of causality, or light touched on it. However, we only dealt with causation based on what can be observed. We have dealt with causality with what can be observed by the senses at some time. Thus, if I were to use a conditional statement, X→Y, then we can observe both X and Y. But now science has moved on to reasoning where we cannot observe both X and Y. We can only observe Y. What does David Hume have to say on such reasoning?

“Impressions way be divided into two kinds, those of Sensation and those of Reflexion. The first kind arises in the soul originally, from unknown causes.”(ToHN)

Now he is saying that our impressions, divided into sensations (something I did not mention, but does not affect anything that has been said on his position), come from causes that we do not know where from. We cannot know where they come, when our senses do not tell us where they came from. He further adds on something else.

“The only existences, of which we are certain, are perceptions, which being immediately present to us by consciousness, command our strongest assent, and are the first foundation of all our conclusions. The only conclusion we can draw from the existence of one thing to that of another, is by means of the relation of cause and effect, which shews, that there is a connection betweixt them, and that the existence of one is dependent on that of another. The idea of this relation is derived from past experiences (perceptions), by which we find, that two beings are constantly conjoined together, and are always present at once to the mind. But as no beings are ever present to the mind but perceptions; it follows that we may observe a conjunction or a relation of cause and effect between different perceptions, but can never observe it between perceptions and objects (things outside of perception). ‘Tis impossible, therefore, that from the existence or any of the qualities of the former, we can ever form any conclusion concerning the existence of the latter, or ever satisfy our reason in this particular.” (ToHN)

So we find that causality holds between what we observe. I see fire and I see smoke. Thus, crudely, I think that fire caused the smoke. But now, when we invoke a cause of something that we observe, which has no observable cause like smoke has the cause of fire, we can make no conclusion. I cannot know what causes my sensations, and I cannot know what unobservable things, if any, are causing what I observe. Thus, going with this conditional statement of a hypothesis based on deduction, X→Y, we are found to have it really looking like this,  ?→Y.

So we find, with Hume, that when science invokes all these unobservable causes for what we observe, we cannot know if they are true or that they exist. It is completely unknown if atoms are the causes of what we observe in a cloud chamber. But someone might say, “We can have strong evidence that they probably exist, since our hypothesis work so well and have led to many corroborated observations. Their predictions have worked extremely well.”

That seems like an intuitive answer, but it is not a very good one, as Hume would think. Why is that? Because there can be many causes for what we observe, and so we have no reason to accept the hypothesis we have now other than it is the only one we have developed systematically. I have stressed the hypothetical character of science, and so I will give a truth table of such a hypothetical character.

Notice line 1 and 3 of the truth table. Both lines of that truth table show that the consequent is true. However, they both disagree over the truth of the antecedent of the conditional statement. Now the third line shows that there could be a different unobservable leading to the same observable consequent. In fact, from a logical point of view, there are an infinity of other unobservables that lead to the same observable consequent.

Now someone could say, “Yes, for each situation there could be other causes that lead to that specific observation, but we have hypothesis that lead have one cause for many different observations of different sorts.” Yes, this is true. The problem is that the same problem holds. Let us hear what W.V. Quine had to say on this.

“If all observable events can be accounted for in one comprehensive scientific theory- one system of the world, to echo Duhem’s echo of Newton – then we may expect that they can all be accounted for equally in another, conflicting system of the world. We may expect this because of how scientists work. For they do not rest with mere inductive generalizations of their observations : mere extrapolation to observable events from similar observed events. Scientists invent hypotheses that talk of things beyond the reach of observation. The hypotheses are related to observation only by a kind of one-way implication; namely, the events we observe are what a belief in the hypotheses would have led us to expect. These observable consequences of the hypotheses do not, conversely, imply the hypotheses. Surely there are alternative hypothetical substructures that would surface in the same observable ways.”

Jane Enlgish also had this to say on the same issue.

“The problem is this: even if we had all possible observations in the sense of all the observation reports true of the actual world, still there would be alternative scientific theories that explain those observations equally well but are incompatible with each other. To put it another way, if you were to decide you accept all theories that are unrefutable in experience, you would accept a contradiction.”

All these different potential hypothesis, would all have the same observable consequents, and thus cover the same situations, but all have different unobservables. They would also all have the same probability, and so we cannot know which one is true. All we can know is what we observe with our senses. The rest of it would be unknown, it would be ?→Y. All Hume would care about would be that the consequents are true. That is all we can know, and the rest is unknown to us.

There is also one question that Hume asks in his Enquiry, which would itself show that the ideas are not based on experience.

When we entertain, therefore, any suspicion that a philosophical term is employed without any meaning or idea (as is but too frequent), we need but enquire, from what impression is that supposed idea derived? And if it be impossible to assign any, this will serve to confirm our suspicion. By bringing ideas into so clear a light we may reasonably hope to remove all dispute, which may arise, concerning their nature and reality

So when we are told that atoms exist or that atoms do such-and-such, we may ask, “from what impression (sensation) is that supposed idea derived?” The answer will be that it came from streaks in a cloud chamber. But another question would be, “How did you arrive that it was these atoms and not something else?”. In the end, we have nothing to rely on for such an idea. There is no impression, and it is based on relation of ideas that we apply to the senses.

Now there is no matter of fact that atoms caused what we observed in the cloud chamber. It is not based on causality, and it is not even arrived at by observation. It is an invention of the imagination to account for what we do observe, and is a tool that we use to predict to future observations. It also helps in the systematization and organization of all those categorical statements that we do have.

Also, these unobservables would be based on relation of ideas, which means that they are true by definition. This is because science has to give a precise definition to the concepts that they invoke, like mathematicians do, and from these well-defined concepts, come to deduce certain observable consequences. Thus, they are very similar to tautologies. They become formal systems that we change certain parts of the sentences when an observation goes counter what is predicted, and this will help account for the observation or we make an ad hoc addition.

Here is an example of what philosopher of science Ronald Giere has to say on how science has took on the Relation of Ideas that David Hume brings up.

“My use of the term “model” (or “theoretical mode”) is intended to capture current scientific usage-at least insofar as that usage is itself consistent. To this end, I would adopt a form of the “semantic” or definitional view of theories (hereafter, models). On this view, one creates a model by defining a type of system. For most purposes one can simply identify the model with the definition…Viewed as definitions, theoretical models have by themselves no empirical content-they make no claims about the world. But they may be used to make claims about the world. This is done by identifying elements of the models with elements of real systems and then claiming that the real system exhibits the structure of the model. Such a claim I shall call a theoretical hypothesis. These are either true or false. From a logical point of view, the definition of a model amounts to the definition of a predicate. A theoretical hypothesis, then, has the logical form of predication: This is an X, where the corresponding definition tells what it is to be an X.”

David Hume was also a nominalist, and this means that he did not believe that general ideas existed. This is when we abstract certain qualities away from the impressions of the senses, and say that they exist on their own. We find an example of this with George Berkeley, which David Hume also followed.

And as the mind frames to itself abstract ideas of qualities or Modes, so does it, by the same precision or mental separation, attain abstract ideas of the more compounded Beings which include several coexistent qualities. For example, the mind having observed that Peter, James, and John resemble each other in certain common agreements of shape and other qualities, leaves out of the complex or compounded idea it has of Peter, James, and any other particular man, that which is peculiar to each, retaining only what is common to all, and so makes an abstract idea wherein all the particulars equally partake–abstracting entirely from and cutting off all those circumstances and differences which might determine it to any particular existence. And after this manner it is said we come by the abstract idea of Man, or, if you please, humanity, or human nature; wherein it is true there is included colour, because there is no man but has some colour, but then it can be neither white, nor black, nor any particular colour, because there is no one particular colour wherein all men partake. So likewise there is included stature, but then it is neither tall stature, nor low stature, nor yet middle stature, but something abstracted from all these. And so of the rest. Moreover, their being a great variety of other creatures that partake in some parts, but not all, of the complex idea of Man, the mind, leaving out those parts which are peculiar to men, and retaining those only which are common to all the living creatures, frames the idea of Animal, which abstracts not only from all particular men, but also all birds, beasts, fishes, and insects. The constituent parts of the abstract idea of animal are body, life, sense, and spontaneous motion. By Body is meant body without any particular shape or figure, there being no one shape or figure common to all animals, without covering, either of hair, or feathers, or scales, &c., nor yet naked: hair, feathers, scales, and nakedness being the distinguishing properties of particular animals, and for that reason left out of the ABSTRACT IDEA. Upon the same account the spontaneous motion must be neither walking, nor flying, nor creeping; it is nevertheless a motion, but what that motion is it is not easy to conceive.

What science does it it abstracts away certain qualities in our impressions, and says that they exist away from what we experienced. These are things like shape, motion, and existing in space. However, we have no experience that such things exist, or that it is as said. They are just abstract ideas that have no basis on experience, and are not based on causality but relation of ideas. Science uses these in creating some of their hypothesis, and are thus unobservable, since we only experience them with colors and etc. They are not based on complex impressions, let alone simple impressions. Thus, these are complex ideas that are not based on anything but the imagination.

So what would Hume think of Modern Science? He would think of it is not based on impressions but based on imagination. This comes back to Hume’s’ quote, “This is the universe of the imagination, nor have we any idea but what is there produced.”

All Hume would care about, and could accept, was that it had true predictions. That means no matter what the hypothesis talked about, the only thing that mattered was that the predictions worked. That is all we could ever know, and that is what was most important, since it had direct results on the world that we know and move in. We do not know if the unobservables exist or not, and it does not matter. All that matters is that we use the hypothesis as instruments to organize our experiences and predict our experiences. Once the hypothesis leads to an observable result, we can use induction from there on out.

Here is a quote from Alfred J. Freddoso talking on David Hume’s views of science.

“Empiricist view (of science): Accepting a scientific theory should involve believing only that the theory is an accurate guide to what is observable and what will be observable in the future — -the aim of natural science is just to order our experience and not to get to real causes.”

We can probably see what Hume would say about science with this quote from Stephen Hawking in his new book The Grand Design.

“But different theories can successfully describe the same phenomenon through disparate conceptual frameworks. In fact, many scientific theories that had proven successful were later replaced by other, equally successful theories based on wholly new concepts of reality…According to model-dependent realism, it is pointless to ask whether a model is real, only whether it agrees with observation.”

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