=Nature of Consciousness.=--Our previous study of the nature of experience has shown that various kinds of conscious states may arise in the mind, now the smell of burning cloth, now the sound of a ringing bell, now the feeling of bodily pain, now a remembered joy, now a future expectation or a resolution. Such a conscious state was seen, moreover, to represent on the part of the mind, not a mere passive impression coming from some external source, but an active attitude resulting in definite experience. It signifies, in other words, a power to react in a fixed way toward impressions, and direct our conduct in accordance with the resulting states of consciousness. Consciousness in the individual implies, therefore, that he is aware of phenomena as they are experienced, and is able to modify his behaviour accordingly. =Types of Consciousness.=--Although allowable, from the standpoint of the learning process, to describe a conscious state as an attitude of awareness in which the individual grasps the significance of an experience in relation to his own needs; it must be recognized that not all consciousness manifests this meaningful quality, or this relation to a felt aim, or end. While lying, for instance, in a vague, half-awake state, although one is conscious, the mental condition is quite devoid of the meaningful quality referred to, and entirely lacks the feeling of reaction, or of mental effort. In this case there is no distinct reference to the needs of the self, and a lack of that focusing of attention necessary to give the consciousness a meaning and purpose in the life of the individual. All such passive, or effortless, states of consciousness, which make up those portions of mental existence in which no definite presentation seems to hold the attention, although falling within the sphere of the scientific psychologist, may nevertheless be left out of consideration in a study of educational psychology. Learning involves apperception, and apperception is always giving a meaning to new presentations by actively bringing old knowledge to bear upon them. For the educator, therefore, psychology may be limited to a study of the definite states of consciousness which arise through an apperceiving act of attention, that is, to our states of experience and the processes connected therewith. For this reason, psychology is by some appropriately enough defined as the science of experience.