David Hume wrote that faint images in thinking are ideas. Impressions are less faint but simpler and are from experience. Complex ideas need not resemble impressions such as abstractions . Among ideas, those that contain the original vivacity of impressions are memory and imagination.
Cause and Effect
We can only know cause and effect from experience, not reasoning or reflection. The statement ‘what begins must have a cause’, he says, is not one that has intuitive certainty, like the statements of logic. As he puts it: ‘There is no object, which implies the existence of any other if we consider these objects in themselves, and never look beyond the ideas which we form of them.’
Hume argues from this that it must be experience that gives knowledge of cause and effect, but that it cannot be merely the experience of the two events A and B which are in a causal relation to each other. It must be experience, because the connection is not logical; and it cannot be merely the experience of the particular events A and B, since we can discover nothing in A by itself which should lead to produce B. The experience required, he says, is that of the constant conjunction of events of the kind A with events of the kind B. He points out that when, inexperience, two objects are constantly conjoined, we do in fact infer one from the other. (When he says ‘infer’, he means that perceiving the one makes us expect the other; he does not mean a formal or explicit inference.) ‘Perhaps, the necessary connection depends on the inference,’not vice versa. That is to say, the sight of A causes the expectation of B, and so leads us to believe that there is a necessary connection between A and B. The inference is not determinedby reason, since that would require us to assume the uniformity of nature, which itself is not necessary, but only inferred from experience.
Bertrand Russell, A History of Western Philosophy
Bertrand Russell, A History of Western Philosophy
‘Objects have no discoverable connexion together;nor is it from any other principle but custom operating upon the imagination, that we can drawany inference from the appearance of one to the experience of another.’
He repeats the contention that what appears to us as necessary connection among objects is really only connection among the ideas of those objects: the mind is determined by custom, and ”tis this impression, or determination, which affords me the idea of necessity’. The repetition of instances, which leads us to the belief that A causes B, gives nothing new in the object, but in the mind leads to an association of ideas; thus ‘necessity is something that exists in the mind, not in object.
‘The sceptic still continues to reason and believe, even though he asserts that he cannot defend his reason by reason; and by the same rule he must assent to the principle concerning the existence of body, tho’ he cannot pretend by any arguments of philosophy to maintain its veracity … We may well ask, what causes us to believe in the existence of body? But ’tis vain to ask, whether there be body or not? That is a point,which we must take for granted in all our reasonings.
Bertrand Russell, A History of Western Philosophy
The Consequences of Humian Skepticism
There is no reason for studying philosophy, according to Hume, except that, to certain temperaments, this is an agreeable way of passing the time.
Hume forgets all about his fundamental doubt; he is careless with regards to his doubts. His skepticism is insincere. Since he cannot maintain it in practice. It has this awkward consequence, that it paralyses every effort to prove one line of action better than another.
It was inevitable that such a self-refutation of rationality should be followed by a great outburst of irrational faith. The quarrel between Hume and Rousseau is symbolic: Rousseau was mad but influential, Hume was sane but had no followers. Subsequent British empiricists rejected his scepticism without refuting it; Rousseau and his followers agreed with Hume that no belief is based on reason, but thought the heart superior to reason, and allowed it to lead them to convictions very different from those that Hume retained in practice. German philosophers,from Kant to Hegel, had not assimilated Hume’s arguments. I say this deliberately, in spite of the belief which many philosophers share with Kant, that his Critique of Pure Reason answered. Hume. In fact, these philosophers—at least Kant and Hegel—represent a pre-Humian type of rationalism, and can be refuted by Humian arguments. The philosophers who cannot berefuted in this way are those who do not pretend to be rational, such as Rousseau,Schopenhauer, and Nietzsche.
Bertrand Russell, A History of Western Philosophy
The growth of unreason in the nineteenth and twentieth century is a natural sequel to Hume’s destruction of empiricism. It is therefore important to discover whether there is any answer to Hume within the framework of an empirical philosophy. If not, there is no intellectual difference between sanity and insanity. The lunatic who believes that he is a poached egg is to be condemned because he is in the minority—on the ground that the government does not agree with him. This is a desperate philosophy, we should hope that there is a way to overcome it.