The leading problems of vocational psychology we have seen to be three in number: First, how may the individual achieve the most adequate knowledge of his own peculiar mental and instinctive constitution, his equipment of capacities, tendencies, interests and aptitudes, and the ways in which he compares, in these respects, with his fellows? Second, how may the individual acquire information concerning the general or special traits required for successful participation in the various vocations, in order to select a line of activity for which he is constitutionally adapted? Third, how may the employer determine the relative desirability, fitness and promise of those who may offer themselves as his associates and assistants, or for minor positions in his employ? Obviously, if vocational psychology were in its maturity, rather than in its infancy, these various questions would resolve themselves into a single problem. The traits required in the various types of work would be fully known and specified, so that both the choice of the individual and the selection by the employer would proceed directly, once the individual's characteristics were known. From this goal we are very far, but by no means hopelessly, removed. As we have seen in the preceding chapters, the line of attack is being advanced very unevenly at its various points. It is indeed characteristic of any new branch of science that it does not advance symmetrically and at a uniform rate, but moves ahead, now in this direction, now in that, so that the line of complete development is some distance behind the outposts of exploration. So in the case of vocational psychology we may draw a rough line which shall represent the main region of advance, and may indicate the various points where the line lags behind or goes conspicuously forward.