John Holland's Contributions: A Theory-Ridden Approach to Career Assistance‪.‬

********** Holland's theory, assessment instruments, and intervention tools transformed the delivery of vocational assistance by counselors, schools, and impersonal mechanisms. This occurred because of the organizing power of his theory of persons and environments, the case with which the theory can be communicated to counselors and clients, and the self-directed nature of the interventions and assessments he developed. This influence on counseling is due partly to the results of a long-term program of science in the pursuit of solutions to practical problems in vocational counseling and partly to the creativity and craft of an author devoted to helping clients understand themselves, their vocational alternatives, and their career situations.