Psychology as the natural history of the various attitudes and structures through which experiencing passes, as an account of the conditions under which this or that attitude emerges, and of the way in which it influences, by stimulation or inhibition, production of other states or conformations of reflection, is indispensable to logical evaluation the moment we treat logical theory as an account of thinking as a response to its own generating conditions, and consequently judge its validity by reference to its efficiency in meeting its problems. The historical point of view describes the sequence; the normative follows the history to its conclusion, and then turns back and judges each historical step by viewing it in reference to its own outcome. In the course of changing experience we keep our balance in moving from situations of an affectional quality to those which are practical or appreciative or reflective, because we bear constantly in mind the context in which any particular distinction presents itself. As we submit each characteristic function and situation of experience to our gaze, we find it has a dual aspect. Wherever there is striving there are obstacles; wherever there is affection there are persons who are attached; wherever there is doing there is accomplishment; wherever there is appreciation there is value; wherever there is thinking there is material-in-question. We keep our footing as we move from one attitude to another, from one characteristic quality to another, because of the position occupied in the whole movement by the particular function in which we are engaged. The distinction _between_ each attitude and function and its predecessor and successor is serial, dynamic, operative. The distinctions _within_ any given operation or function are structural, contemporaneous, and distributive. Thinking follows, we will say, striving, and doing follows thinking. Each in the fulfilment of its own function inevitably calls out its successor. But coincident, simultaneous, and correspondent _within_ doing is the distinction of doer and of deed; _within_ the function of thought, of thinking and material thought upon; within the function of striving, of obstacle and aim, of means and end. We keep our paths straight because we do not confuse the sequential and functional relationship of types of experience with the contemporaneous and structural distinctions of elements within a given function. In the seeming maze of endless confusion and unlimited shiftings, we find our way by the means of the stimulations and checks occurring within the process in which we are actually engaged. Operating within empirical situations we do not contrast or confuse a condition which is an element in the formation of one operation with the status which is one of the distributive terms of another function. When we ignore these specific empirical clues and limitations, we have at once an insoluble, because meaningless, problem upon our hands.