But, it is said, the very process of thinking makes a certain assumption regarding the nature of reality, viz., that reality is self-consistent. This statement puts the end for the beginning. The assumption is not that “reality” _is_ self-consistent, but that by thinking it may, for some special purpose, or as respects some concrete problem, attain greater consistency. Why should the assumption regarding “reality” be other than that specific realities with which thought is concerned are _capable of receiving_ harmonization? To say that thought must assume, in order to go on, that reality already possesses harmony is to say that thought must begin by contradicting its own direct data, and by assuming that its concrete aim is vain and illusory. Why put upon thought the onus of introducing discrepancies into reality in order just to give itself exercise in the gymnastic of removing them? The assumption that concrete thinking makes about “reality” is that things just as they exist may acquire _through activity, guided by thinking_, a certain character which it is excellent for them to possess; and may acquire it more liberally and effectively than by other methods. One might as well say that the blacksmith could not think to any effect concerning iron, without a Platonic archetypal horseshoe, laid up in the heavens. His thinking also makes an assumption about present, given reality, viz., that this piece of iron, through the exercise of intelligently directed activity, may be shaped into a satisfactory horseshoe. The assumption is practical: the assumption that a specific thing may take on in a specific way a specific needed value. The test, moreover, of this assumption is practical; it consists in acting upon it to see if it will do what it pretends it can do, namely, guide activities to the required result. The assumption about reality is not something in addition to the idea, which an idea already in existence makes; some assumption about the possibility of a change in the state of things as experienced _is_ the idea--and its test or criterion is whether this possible change can be effected when the idea is acted upon in good faith.