precise points in which they agree from those in which they disagree, and in this way to explain why a certain result should follow in one case and a different result in another case. Causality in this sense can only exist for the ideational consciousness, and the development of the ideational consciousness in this direction is a development of conceptual thinking--of generalization.” Wherein, then, lies the central core of truth in Professor Groos’s contention? In the satisfaction that arises from the success of any conative activity. We see that the animal striving and doing falls within our conception of a cause, in the scientific sense of the word,--a relatively constant and continuous antecedent of diverse sequent effects. We infer that pleasure accompanies the satisfaction of the multifarious conative impulses. The pleasure is the animal’s; the conception of causality and of self as a continuous person, still the same amid diversity of conscious situations, is ours. If we bear this in mind there can be no objection to our attributing to animals joy in ability or power. It is the pleasure derived from that successful conation whereby animals fall into the category of causes within the scheme of our rational thought. In fighting-play and hunting-play, too, there arise in more specific forms the pleasures of successful conation with the antithetical feelings accompanying thwarted conation. And these are distinguished from earnest, partly because the companion or the inanimate substitute for prey is the centre of a different situation from that afforded by an enemy or the natural object of the chase; partly by the absence of certain insistent emotional states which characterize earnest and the serious business of life. In fighting, this is anger. And we often see the tendency of this to arise in the midst of fighting-plays, and at once say that it becomes serious and passes into fighting in earnest. Indeed, some tinge of earnest, with its fuller emotional tone, forms part of the preparation for future life, and so far falls within the definition Professor Groos gives of play. From which we may see that play is not easily marked off from other forms of conation. Brief reference to the element of “make-believe,” which Dr. Groos assigns to the higher forms of play, may be reserved for our fourth section; and some further discussion of its psychological aspect to the concluding chapter. III.--COURTSHIP