The formulation of ideas of experienced objects in terms of measured quantities, as these are established by an inten- tional art or technique, does not say that this is the way they must be thought, the only valid way of thinking them. It states that for the purpose of generalized, indefinitely exten- sive translation from one idea to another, this is the way to think them. The statement is like any other statement about instruments, such as that so-and-so is the best way of sending anumber of telegraphic dispatches simultaneously. As far as it is actually the best instrumentality, the statement is correct. It has to be proved by working better than any other agency jit is in process of continuous revision and improvement. For pur- poses except that of general and extensive translation of one conception into another, it does not follow that the "scientific" way is the best way of thinking an affair. The nearer we come to an action that is to have an individualized unique object of experience for its conclusion, the less do we think the things in question in these exclusively metric terms. The physi- cian in practice will not think in terms as general and abstract as those of the physiologist in the laboratory, nor the engineer in the field in those as free from special application as will the physicist in his work-shop. There are many ways of think- ing things in relation to one another jthey are, as conceptions, instruments. The value of an instrument depends upon what is to be done with it. The fine scale micrometer which is indis- pensable in the successful performance of one operation would be ahindrance in some other needed actj and awatch spring is useless to give elasticity to amattress.