A practical belief is what a man proposes to go upon. A decision is more or less pressing. What ought it to be? That must depend upon what the purpose of his action is. What then, is the purpose of a man? That is the question of pure ethics, a very great question which must be disposed of before the logic of practical belief can be entered upon to any good effect.
A state of belief in a proposition is such a state that the believer would on every pertinent occasion act according to the logical consequence of that proposition, He has a habit, and the proposition describes in abstract terms what sort of a habit it is. But for genuine belief, the man must not only have the habit, but must be aware of having it, and must be fully satisfied with having it. I will not say that no more than that is involved in saying that a man believes a proposition, but I think we may say that that constitutes practical belief.
A practical belief may […] be described as a habit of deliberate behavior. The word “deliberate” is hardly completely defined by saying that it implies attention to memories of past experience and to one’s present purpose, together with self-control. The acquisition of habits of the nervous system and of the mind is governed by the principle that any special character of a reaction to a given kind of stimulus is (unless fatigue intervenes) more likely to belong to a subsequent reaction to a second stimulus of that kind, than it would be if it had not happened to belong to the former reaction. But habits are sometimes acquired without any previous reactions that are externally manifest. A mere imagination of reacting in a particular way seems to be capable after numerous repetitions of causing the imagined kind of reaction really to take place upon subsequent occurrences of the stimulus. In the formation of habits of deliberate action, we may imagine the occurrence of the stimulus, and think out what the results of different actions will be. One of these will appear particularly satisfactory; and then an action of the soul takes place which is well described by saying that that mode of reaction “receives a deliberate stamp of approval.” The result will be that when a similar occasion actually arises for the first time it will be found that the habit of really reacting in that way is already established. I remember that one day at my father’s table, my mother spilled some burning spirits on her skirt. Instantly, before the rest of us had had time to think what to do, my brother, Herbert, who was a small boy, had snatched up the rug and smothered the fire. We were astonished at his promptitude, which, as he grew up, proved to be characteristic. I asked him how he came to think of it so quickly. He said, “I had considered on a previous day what I would do in case such an accident should occur.” This act of stamping with approval, “endorsing” as one’s own, an imaginary line of conduct so that it shall give a general shape to our actual future conduct is what we call a resolve. It is not at all essential to the practical belief, but only a somewhat frequent attachment.
[—] If an opinion can eventually go to the determination of a practical belief, it, in so far, becomes itself a practical belief; and every proposition that is not pure metaphysical jargon and chatter must have some possible bearing upon practice. [—]
…there is just this difference between a practical belief and an expectation so far as it involves no purpose [or] effort; namely that the former is expectant of muscular sensation, the latter of sensation not muscular.