The historical experience of development of medical science is indicative of the close association of structurally-morphological and causal concepts in the theory of pathology. The former and the latter become closer. This gives grounds to distinguish the concept of morphological determinism as a system of universal associations intrinsic in the host and determining its reactions to the environmental effects. Morphological determining allows proper understanding of the integrity of a living organism, its structural organization, and substantiates the principle of the unity of the structure (morphology) and dynamics (functioning) in the theory of pathology. Synchronously and concomitantly running structural-morphological equivalent processes are always at the basis of all the functional changes. Therefore the concepts of the primary nature of functional and secondary nature of structural-morphological changes currently cannot be accepted to be correct, and the concept of functional diseases should be refuted as ungrounded. The cognitive value of morphological determinism is in that it orients the thinking and actions of physician towards the elucidation of the structure of a pathological process and brings each functional change to the appropriate morphological foundation at different levels of the organization of a living being down to the molecular level.