A Treatise of Human Nature Additional Summary

David Hume

The Limits of Experience

Hume next questions whether we possess any evidence that this principle is true, or that it has to be true. Since we can readily imagine that the world might change in many respects in the future, it is not possible to demonstrate that nature must be uniform. Our experience up to the present moment does not constitute evidence as to what the future course of nature will be, or must be. Just because the sun has risen every day up to now does not prove that it has to rise tomorrow. We can judge the future only if we know that nature is uniform. However, our information up to this point is only that, so far, nature has always been uniform. Experience can provide us with no clue about what has to be the case in the future. Hence, we can neither demonstrate nor prove from experience that the all-important principle of the uniformity of nature is true, even though much of our reasoning about the world depends upon it.

The acceptance of this principle, Hume contends, is a fundamental characteristic of human nature. We have a habit or custom that operates upon us for unknown and unknowable reasons. After we have experienced the same sequence of conjoined events several times, then, when we perceive one of the conjuncts, habit or custom leads us to think of the other, and to think of it in a lively and forceful way. Although we are able to think of any idea we wish, we are led psychologically to think only of a particular conjoined idea and to conceive of it with some of the force and vivacity of its conjoined impression. Such force and vivacity constitute our belief in the actual occurrence of the conjoined item. In terms of this explanation, the principle of the uniformity of nature is more a principle about how we think and feel than it is one about the order of events in the world.

Causation Rooted in Imagination

Hume uses his discovery of the psychological origins of our belief in the uniformity of nature to explain the basis for our conviction that there is a necessary connection between events. The necessary connection is never perceived, no matter how often the same sequence is observed. However, after a constant conjunction of events has been perceived many times, we then feel that one of the conjuncts causes or produces the other. It is not any discoverable fact about the events that makes us believe this, but rather our psychological attitude toward the events. We possess a fundamental propensity or determination of the mind to think of a conjoined idea after experiencing the conjunct or thinking of it, once we have perceived the constant conjunction of the two in our experience. This determination, which is a strong feeling, is the necessary connection that we think exists between events. Although it is felt in us, we have a tendency to conceive of it as existing in the events themselves. This idea is actually a feature of the way we think about events, rather than a feature of them. Thus, the term “cause” can be defined as “An object precedent and contiguous to another, and so united with it in the imagination, that the idea of the one determines the mind to form the idea of the other, and the impression of the one to form a more lively idea of the other.”

Knowledge vs. Belief

In Hume’s explanation of causality, he joins Nicolas de Malebranche’s contention that there is no necessary connection between events with his own psychological account of how we react to the uniformities in experience. Because of our habits, we expect the future to resemble the past, and we feel that when we observe certain events, their constant conjuncts must also be taking place, even if we cannot observe them. We have no actual knowledge of what is taking place, but only beliefs. Because we can never be completely sure that our beliefs correspond to the actual state of affairs, our causal information is always, at best, only probable.

Hume sees the task of the sciences as that of carefully establishing bases for “reasonable belief” by collecting data about the constant conjunctions that occur in human experience and organizing these data in terms of scientific laws. These laws provide a form of rational expectation in that they allow us to predict the future course of events on the basis of detailed information about what has happened up to now. The scientist, like anyone else, expects, through personal habits and propensities, that the future will resemble the past. Science, for Hume, is not the search for the “real” cause of events but for the best available probable predictions about the course of nature, founded on correlations of constant conjunctions of events and the psychological habits of human beings.

Hume’s Skepticism

After presenting his explanation of the source of our information, the nature of our beliefs about the world, and the character of scientific “knowledge,” Hume turns in part 4 of A Treatise of Human Nature to the full statement of his skeptical views. He first presents a series of reasons to show why we should be doubtful of the conclusions that we come to because of our reasoning and those that we come to because of our sense experience and our attitudes toward it. Then Hume contends that though there are basic difficulties with regard to both our reason and our senses, we still have to believe many things because of our psychological structure. Unfortunately, what we believe is often either indefensible or...

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The Limits of Skepticism

However, nature prevents us from carrying out this skeptical attitude to its final destructive conclusion. Regardless of the difficulties, in practice we find that we have to believe all sorts of things, even incompatible things. When we go out in the world, the skeptical doubts lose their force; we are overwhelmed by our natural feelings and beliefs, and we act and live in the same way anyone else does. Hume’s final advice is that one should be skeptical when one has to be, and be a natural believer when one must, while realizing that neither of these attitudes has any final justification. In periods when doubts are not being taken seriously, one can go on to examine other aspects of the human world, as Hume does in books 2 and 3 of A Treatise of Human Nature, and search for laws about human passions. (One of his findings in this regard is that reason is, and ought only to be, the slave of the passions.)

A Treatise of Human Nature has been a rich source of many contemporary views. The more empirical side of it has greatly influenced the logical positivists and the language analysts. Some of the psychological analysis of human belief and behavior has influenced the pragmatists and instrumentalists. The extreme skepticism and irrationalism have had some impact on neo-orthodox theologians. It is for these reasons that A Treatise of Human Nature is regarded by many as one of the best philosophical works in the English language.

Bibliography

Additional Reading

Ayer, A. J. Hume. New York: Hill and Wang, 1980. This brief introduction to Hume’s life is both well written and useful. The chapter on aims and methods is especially good.

Chappell, V. C., ed. Hume: A Collection of Critical Essays. Garden City, N.Y.: Doubleday, 1966. This collection of twenty-one essays by such acknowledged authorities as Ernest Mossner and Anthony Flew is valuable to students of Hume.

Hanson, Delbert J. Fideism and Hume’s Philosophy: Knowledge, Religion, and Metaphysics. New York: Peter Lang, 1993. Fideism holds that belief in some...

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