We shall meet the determining tendencies again, when we come to deal with action and thought. Meantime let us note that they furnish a definition of that rather obscure word ‘suggestion.’ A =suggestion= is something that comes to us with more or less of the force of a command; but what does this ‘force of a command’ mean? Our new technical term helps us: a suggestion is _any stimulus to nervous activity, external or internal, with or without mental accompaniment, that touches off a determining tendency_. The determining tendency may be realised, or may be inhibited, as circumstances decide; the essence of a suggestion is, always and everywhere, that it releases such a tendency. Thus, the psychological observer of whom we spoke on p. 96 received from the experimenter certain instructions; these instructions were obeyed, that is, they were effective suggestions. What, now, set up the determining tendency to follow instructions? A foregone suggestion: the student came into the laboratory to observe, to be taught, to put himself under direction. What brought him into the laboratory? Another foregone suggestion: the wish to learn psychology at first hand, the example of his friends. What led him to choose at the university the course that includes psychology? What led him to choose this particular university? What led him to enter any university? All these results are due to suggestions, which grow in number and complexity the farther back we go; and the force of the suggestions, in every case, is their appeal to determining tendencies. A nervous system that lacked these tendencies would furnish its possessor with connections that were all, so to speak, on the same plane; the organism could neither lead nor follow, neither choose nor reject, neither work nor play; it would not be suggestible. From this digression we pass to the study of emotion, which, as we have seen, is closely related to the instincts of the middle part of our scale.