_Doctrine of the Predicate._ So long as logicians are permitted to fabricate their own examples, all is plain sailing with the syllogism. But they are sometimes obliged to deal with genuine arguments. In this case what they do is to assume that _for logical purposes_ every predicate of the precedent--that is, the applicate--is a general or class term. Even when an argument is good they spoil it with a bad theory. Sir William Hamilton states that up to his time logicians recognised but one type of proposition--that called by him the proposition 'in extension,' which means the classifying of the subject. He announced that he intended to introduce a proposition 'in comprehension,' meaning a judgment in the category of inherence--as for instance, 'man is responsible.' He further said that he recognised a third type of proposition, that concerning 'cause and effect.' But in the course of working out these logical novelties he seems to have discovered that they were irreconcilable with conversion, and so he dropped them. The judgment in comprehension, he then declared, was to all intents and purposes the same as one in extension, and as to causation--why, a cause is a class, and an effect is an individual belonging to that class![22] Let us see what is the result of treating applicates as general ideas. Take an example in each of the categories. 'The paper is white.' This means that the paper has the property or attribute of whiteness. In logic it is interpreted to mean that paper is an individual of the class _white_. This is wrong, for there is no such class. No sane person would form a class out of salt, snow, milk, china, silver, the moon, and other white things; for though they have a common property it is not the sign of a common human utility. The confusing a single property with a class is not always owing to exigencies of syllogism. It pervades the writings of most Western metaphysicians, and may be accounted for in this manner. General ideas and abstract properties or ideas have in common that they are _partial_ recognitions of what we perceive (XIV). The partition in each is however made in a different way, and for a different purpose. In generalisation the selection is done almost mechanically. We see many things that have some common relation, function, or utility for us, and we remember only so much of them as appears to be necessary for the recognition of that relation or utility--just so much of the Intellectual experience as has always accompanied the Sentimental experience. The process is very like that of putting a piece of wood or ivory in a turning-lathe, and whittling off all that we do not want. A general idea is the useful core of a multitude of superposed observations, each of which had something irrelevant--something which it is better to forget. We whittle this off and remember only the core.