Would you know the sentiments, inclinations, and course of life of the Greeks and Romans? Study well the temper and actions of the French and English: You cannot be much mistaken in transferring to the former most of the observations which you have made with regard to the latter. Mankind are so much the same, in all times and places, that history informs us of nothing new or strange in this particular. Its chief use is only to discover the constant and universal principles of human nature, by showing men in all varieties of circumstances and situations, and furnishing us with materials from which we may form our observations and become acquainted with the regular springs of human action and behaviour. These records of wars, intrigues, factions, and revolutions, are so many collections of experiments, by which the politician or moral philosopher fixes the principles of his science, in the same manner as the physician or natural philosopher becomes acquainted with the nature of plants, minerals, and other external objects, by the experiments which he forms concerning them. Nor are the earth, water, and other elements, examined by Aristotle, and Hippocrates, more like to those which at present lie under our observation than the men described by Polybius and Tacitus are to those who now govern the world.Hume notes that history is a guide to human behavior only for the most part, but puts this down to "the diversity of characters, prejudices, and opinions". He goes on:
The vulgar, who take things according to their first appearance, attribute the uncertainty of events to such an uncertainty in the causes as makes the latter often fail of their usual influence; though they meet with no impediment in their operation. But philosophers, observing that, almost in every part of nature, there is contained a vast variety of springs and principles, which are hid, by reason of their minuteness or remoteness, find, that it is at least possible the contrariety of events may not proceed from any contingency in the cause, but from the secret operation of contrary causes. This possibility is converted into certainty by farther observation, when they remark that, upon an exact scrutiny, a contrariety of effects always betrays a contrariety of causes, and proceeds from their mutual opposition.If we agree with Hume then we might wonder whether any social science beyond history could possibly be needed. Psychology, economics, and history would all seem to blend into one science of human behavior, based, of course, on observation of past behavior. There is some evidence of this happening, in fact, with economists offering to explain more and more kinds of behavior and the emergence of "behavioral economics," which looks a lot like psychology but pays better. (Of course it can also be argued that economists don't always pay as much attention to history as they should.)
On the other hand, we might dispute Hume's implication that human behavior can be explained by discovering hidden springs and principles. Are we really as machine-like as this image suggests?
Hume does not say that we are machines:
Thus it appears, not only that the conjunction between motives and voluntary actions is as regular and uniform as that between the cause and effect in any part of nature; but also that this regular conjunction has been universally acknowledged among mankind, and has never been the subject of dispute, either in philosophy or common life. Now, as it is from past experience that we draw all inferences concerning the future, and as we conclude that objects will always be conjoined together which we find to have always been conjoined; it may seem superfluous to prove that this experienced uniformity in human actions is a source whence we draw inferences concerning them. But in order to throw the argument into a greater variety of lights we shall also insist, though briefly, on this latter topic.The connection between motives and actions is said here to be merely like the connection between cause and effect. But Hume does go on to say that human actions are just as governed by necessity as any other event. This is partly because we are more predictable than we might like to admit, and partly because causation in other parts of nature has less to it than we might imagine. There is, he says, no idea of causation and necessity other than "the constant conjunction of objects, and the consequent inference of the mind from one to another." Since we find the same constant conjunction and inference from one to the other with motives and actions (other things being equal) there can be no justification for denying that human behavior is just as predictable as the behavior of inanimate objects.
It is hard to disagree with Hume here. But not impossible. Wittgenstein questions the idea of causation as constant conjunction on the grounds that it might be quite clear from just one case that one thing was causing another. For instance, if I see a string moving across the floor I might investigate and find that someone is pulling it. Is there, must there be, experience of pulling events being constantly conjoined with being-pulled events? As I recall Bill Brenner has used the example of cutting a cake. The cutting is not conjoined with the being cut as one event might be conjoined with another, distinct event.
There seem to be two points here. One is that cause and effect are not always as distinct as they are in the cases that Hume apparently has in mind. The other is that we seem to be able to identify something as a cause from just one experience. This is most obviously true in cases where the effect is not distinct from the cause.
On p. 373 of Philosophical Occasions Wittgenstein says:
We react to the cause.
Calling something 'the cause' is like pointing and saying: 'He's to blame!'
On p. 387 we find the case I had in mind above:
There is a reaction which can be called reacting to the cause.-- We also speak of 'tracing' the cause; a simple case would be, say, following a string to see who is pulling at it. If I then find him--how do I know that he, his pulling, is the cause of the string's moving? Do I establish this by a series of experiments?
If I were to try to use this as the basis of an argument against Hume he might say that I see this as a case of causation because I am familiar with a general pattern of which this case is an instance. But, Wittgenstein might counter, how did I ever become aware of this general pattern?
The origin and the primitive form of the language is a reaction; only from this can more complicated forms develop.
Language--I want to say--is a refinement. "In the beginning was the deed." (p. 395)
The difference between Hume and Wittgenstein here is quite subtle. Both see a reaction as essential to the development of the concept of causation. Hume emphasizes the reaction to a pattern, Wittgenstein just the reaction itself, which need not (although he does not insist on this) be to a pattern or series.
Hume's hypothesis that we identify events of type x as causes of events of type y after some habituation is plausible, but I don't know how this would be proved. How long must the series of conjunctions be? Could it consist of just one instance? That does seem possible. Something hurts your hand and you turn and look in that direction. Doesn't that happen, even with babies and animals? Isn't this a kind of association of cause (something over there) and effect (this pain)? If we want to investigate the psychological foundation of the concept of causation, as I think Hume does, then this kind of thing is surely relevant. It might not be rational to think that x causes y after just one episode of y's following x, but we are not that rational, as Hume showed. And of course we might be wrong. But we do sometimes behave and think as if x causes y after just one case of the two being conjoined. And in some cases it is hard even to divide cause and effect into two in the first place.
The point about reacting in a blaming-like way is important too. there is a kind of judgement, or something like judgement, involved in identifying one thing as the cause of another. David Cockburn is good on this in his book An Introduction to the Philosophy of Mind. As I recall one of the points he makes there is that to judge that a particular event or set of events is the cause of some other event is, in part, to judge that event or those events to be the relevant factor in understanding why the event in question occurred. This kind of judgement of relevance is not a simple reading of the facts presented by the world.
What are the implications for social science? Hume suggests that we can find patterns in human behavior, and that doing so might/would constitute a science. Wittgenstein seemingly thinks that we might not even find patterns and that what we find will depend on some judgments on our part.
I have not shown at all conclusively that Wittgenstein is right. But whether it matters depends on what we want from a social science, and I think that is the question to try to answer before worrying about whether we can have it.