LATER PHASES IN MENTAL DEVELOPMENT 59 
We may say, then, that the higher phases of mental 
development are characterized by the fact that the situations 
contain the products of reflective thought, presumably absent 
in the earlier stages ; they are further characterized by a new 
purpose or end of consciousness, namely, to explain the 
situations hitherto merely accepted as they are given in pre- 
sentation or re-presentation; they require deliberate attention 
to the relationships which hold good among the several 
elements of successive situations ; and they involve, so far as 
behaviour is concerned, the intentional application of an ideal 
scheme with the object of rational guidance. We shall follow 
Dr. Stout in terming this later stage of mental development 
the ideational stage ; and in speaking of the simpler situations 
considered in the preceding section as belonging to the 
perceptual stage. 
It should be observed that we are not attempting to 
determine just where, in the scale of organic existence, the line 
between the perceptual and the ideational stages of mental 
development is to be drawn. We are certainly very far from 
asserting that the one does not give rise to the other in the 
course of an evolution which is orderly and progressive. We 
are merely contrasting the rational guidance of effective 
consciousness at its best with the earlier embryonic condition 
out of which it has arisen by natural genesis. In doing this 
we have been forced to make some reference to the difficulties 
of technical nomenclature. And some further reference is 
necessary lest our point of view be misunderstood. 
We shall regard these abstract and general ideas as the 
products of an intentional purpose directed to the special end 
of isolating the one and of classifying the other; we shall 
reserve the term rational for the conduct which is guided 
in accordance with an ideal scheme or deliberate plan of 
action ; while for behaviour to the guidance of which no such 
reflection and deliberation seems to have contributed we shall 
reserve the term intelligent. If, for example, the rejection of 
a cinnabar caterpillar by the chick is the direct result of 
experience through the re-presentation in the new situation 
