Against the background of contemporary new views, approaches and methods of teaching and training, it is assumed that we are faced with the emergence of a new branch of science, a science of instruction, ‘located’ somewhere between the psychology of learning and educational work. This science of instruction is carefully distinguished from the much discussed technology of education, a term which is reserved for the field of application (praxis) alone. The most characteristic requirement of a science of instruction is that it must provide operational rules, so-called ‘operative precepts’ with reference to well-defined forms of learning. Another fundamental distinction in the paper is made between operative and normative precepts. Examples of certain types of operative precepts are discussed, which in the main have bearing upon the technology of education called programmed instruction; they belong to a body of operative, instructional precepts, which could be traced to a developing science of instruction. Finally some concepts and functions of instruction are dealt with and it is stressed that this field of application, in order to secure the necessary basis of decision, must be rooted on the one hand in a science of instruction capable of developing operative rules, and on the other hand in a philosophy of education whence it can derive its normative precepts.