Charles S. Peirce
Chapter V. That The Significance Of Thought
Lies In Its Reference To The Future
MS 239 (Robin 392, 371): Writings 3, 107-108
In every logical mind there must be 1st, ideas; 2nd, general rules according to which one idea determines another, or habits of mind which connect ideas; and, 3rd, processes whereby such habitual connections are established.
A belief is an habitual connection of ideas. For example, to say that I believe prussic acid is a poison is to say that when the idea of drinking it occurs to me, the idea of it as a poison with all the other ideas which follow in the train of this will arise in my mind. Among these ideas, or objects present to me, is the sense of refusing to drink it. This, if I am in a normal condition, will be followed by an action of the nerves when needed which will remove the cup from my lips. It seems probable that every habitual connection of ideas may produce such an effect upon the will. If this is actually so, a belief and an habitual connection of ideas are one and the same.
In a mind which is capable of logical criticism of its beliefs, there must be a sensation of believing, which shall serve to show what ideas are connected. The recognition that two objects present belong together as one is a judgment. All ideas arise in judgments. This is clearly the case if they are caused by previous ideas. If they are sensations then they at once cause other ideas and are connected with these in judgments. The intellectual value of ideas lies evidently in their relations to one another in judgments and not to their qualities in themselves. All that seems blue to me might seem red and vice versa and yet all that I now find true of those objects I should equally find true then, if nothing else were changed. I should still perceive the same distinctions of things that I do now. The intellectual significance of beliefs lies wholly in the conclusions which may be drawn from them, and ultimately in their effects upon our conduct. For there does not seem to be any important distinction between two propositions which never can yield different practical results. Only the difference in the facility with which a conclusion can be reached from two propositions must be regarded as a difference in their effects upon our actions.
It appears then that the intellectual significance of all thought ultimately lies in its effect upon our actions. Now in what does the intellectual character of conduct consist? Clearly in its harmony to the eye of reason; that is in the fact that the mind in contemplating it shall find a harmony of purposes in it. In other words it must be capable of rational interpretation to a future thought. Thus thought is rational only so far as it recommends itself to a possible future thought. Or in other words the rationality of thought lies in its reference to a possible future.