In sum, then, =attention appears in the human mind at three stages of development=: as primary attention, determined by any stimulus that is biologically powerful; as secondary attention, during which a perception or idea dominates the mind in face of opposition; and as derived primary attention, when this perception or idea has gained practically undisputed ascendency over its rivals. Looking at life in the large, we may say that the period of training or education is a period of secondary attention, and that the following period of mastery and achievement is a period of derived primary attention. Looking at experience more in detail, we see that education itself consists, psychologically, in an alternation of the two attentions; habit is made the basis of further acquisition, and acquisition, gained with effort, passes in its turn into habit; the cycle recurs, so long as the nervous system remains plastic. Secondary attention thus appears as a stage of transition, of conflict, of waste of nervous energy, though it appears also as the necessary preliminary to a stage of real knowledge. Meanwhile and all the while there is no escape from interruption by the original primary attention; but the interruptions grow less and less disturbing as civilisation proceeds. § 21. =The Nature of Attention.=—Our next task, in the words of p. 93, is to _trace the pattern of attention_, to describe as accurately as possible the arrangement of our vivid and obscure sensations. Notice that, in popular parlance, attention covers only the vivid processes of the moment; psychologically, however, the term includes both the vivid and the obscure, those that we are ‘distracted from’ as well as those that we are ‘attending to,’ This being understood, we may attempt a description.