Excerpts from  Wisdom of the Ages 

In the 18th and 19th centuries, the trilogy of the mind was the accepted classification of mental activities throughout Germany, Scotland, England and America. In the first half of the 20th century, it was American psychologist William McDougall who was its primary proponent. 

As Ernest R. Hilgard notes in “The Trilogy of Mind: Cognition, Affection and Conation” (1980), McDougall “assumed that his reader was familiar with the classification of cognitive, affective and conative, as commonsensical and noncontroversial .“ 

In McDougall’s “Outline of Psychology (1923), he refers to the threefaculty concept as “generally admitted.” He said, “We often speak of an intellectual or cognitive activity; or of an act of willing or of resolving, choosing, striving, purposing; or again of a state of feeling. But it is generally admitted that all mental activity has these three aspects, cognitive, affective and conative; and when we apply one of these three adjectives to any phase of mental process, we mean merely that the aspect named is the most prominent of the three at that moment. Each cycle of activity has this triple aspect; though each tends to pass through these phases in which cognition, affection and conation are in turn most prominent; as when the naturalist, catching sight of a specimen, recognizes it, captures it, and gloats over its capture.” 

In his “Analysis of Personality Theories,” Albert Mehrabian (1968) says, “The traditional set of distinctions which have been made regarding the individual relationship to people, objectives or events in his world are cognitive, conative and affection. Cognition.., refers to the ways in which an individual knows various aspects of his world. Conation refers to an individual’s relationship of wanting, wishing or their opposite, toward various aspects of his world. Affection refers to an individual’s relationship of positive versus negative feeling toward various aspects of his world.” 

Stanford University’s Richard E. Snow, writing an editorial entitled “Intelligence for the Year 2001,” (1980) sums up the situation well when he says, “It is not unreasonable to hypothesize that both conative and affective aspects of persons and situations influence the details of cognitive processing . . . A theoretical account of intelligent behavior in the real world requires a synthesis of cognition, conation and affect. We have not really begun to envision this synthesis” (P. 194 “Intelligence for the Year 2001”). 

C. F. Stout (1913) said conation, as goal-directed striving or purposive activity, involved two meanings of the goal or end of the striving. “One is the obtaining of means and the other making affective [sic] use of the means.” 

Kurt Goldstein (1963) included conation in his concept of “Coming to Terms with the World.” He called conation “self-actualization,” the matrix of all motivation of “basic drive” which accounts for all human activity. 

In Freud’s theory of the conative nature of character, he recognized what great novelists and dramatists had always known. That, as Balzac put it, the study of character deals with “The forces by which man is motivated.” That the way a person acts, feels and thinks is, to a large extent, deemed by the specificity of his character and is not merely the rational response to realistic situations. That ~~man’s fate is his character.” 

Abraham Maslow developed his Hierarchy of Needs based on his understanding "that humans were propelled into action by needs that of necessity have to be inborn and thus instinct like. He created a new word 'instinctoid' to differentiate what he was talking about from what is usually understood by instincts." 

Considered the guru of self-actualization, Maslow said that mans seeks " to be true to his own nature, to trust himself, to be authentic, spontaneous, honestly expressive, to look for the sources of his action in his own deep inner nature." Towards A Psychology Of Being 

Conation and human instinctive drives have always been a part of modern psychological theory, if only as an underlying assumption.