We begin therefore with the nature of the psyche as this modern, growing, changing psychology conceives it; for this is the raw material of regenerate man. If we exclude those merely degraded and pathological theories which have resulted from too exclusive a study of degenerate minds, we find that the current conception of the psyche--by which of course I do not mean the classic conceptions of Ward or even William James--was anticipated by Plotinus, when he said in the Fourth Ennead, that every soul has something of the lower life for the purposes of the body and of the higher for the purposes of the Spirit, and yet constitutes a unity; an unbroken series of ascending values and powers of response, from the levels of merely physical and mainly unconscious life to those of the self-determining and creative consciousness.[62] We first discover psychic energy as undifferentiated directive power, controlling response and adaption to environment; and as it develops, ever increasing the complexity of its impulses and habits, yet never abandoning anything of its past. Instinct represents the correspondence of this life-force with mere nature, its effort as it were to keep its footing and accomplish its destiny in the world of time. Spirit represents this same life acting on highest levels, with most vivid purpose; seeking and achieving correspondence with the eternal world, and realities of the loftiest order yet discovered to be accessible to us. We are compelled to use words of this kind; and the proceeding is harmless enough so long as we remember that they are abstractions, and that we have no real reason to suppose breaks in the life process which extends from the infant's first craving for food and shelter to the saint's craving for the knowledge of God. This urgent, craving life is the dominant characteristic of the psyche. Thought is but the last come and least developed of its powers; one among its various responses to environment, and ways of laying hold on experience.