As a scientific discipline grows it fractures into smaller fields of study, with the size of these areas being dictated partly by the nature of the subject, or even joints in nature, but very largely by the competence of those involved. Indeed, the boundary between the relevant areas constantly shifts as the proficiency of its students fluctuates; at one time a field, linguistics for example, will seem on the verge of swallowing the whole of human science, at another it will seem a dependent territory of bio-pyschology.
The competence of an individual is to be defined as a combination of talent, available time, and other practical considerations, such as whether the society in which the worker lives is prepared to finance their work. It is not merely a question of intellectual muscularity and fitness, though this clearly of very great importance. Proficiency is to be defined as the efficient working of a student in a discipline. This can be further explained as the mastery of a sufficiently large part of a field of study that the worker may move around in it with ease, switching jobs.
The difference between competence and proficiency can be explained through the example of a government-funded undergraduate reading natural sciences. This person, who for the sake of argument can be taken as exceptionally able, is competent, but because of ignorance is not yet proficient. As a result of the difficulty in assessing whether someone has passed from one category to another most societies have instituted a University Degree system, which is an intellectually arbitrary way of plotting the position of any individual but has many administrative benefits. The level of proficiency in a field is not fixed, as the relatively recent trend demanding doctorates of all students wishing to pursue research careers tends to show.
The most proficient persons in a field will tend to cluster around one particular area, this being for that time the centre of the sub-discipline. If this centre shifts towards what was the margin of the area it will seem that the whole field is moving. If, as often happens, the centre divides, then field will appear to expand.
Even the most proficient persons will not be able to patrol the borders that they themselves define; too much of their time will be absorbed at the centre. Hence the importance of a large number of students. These people will not only hold and maintain but much more importantly carry messages between fields. It is not possible to be highly proficient in two fields, and this is true by definition, since if someone were ambidextrous in this way it would mean that the fields had been drawn together, and in practice this never happens, the process being one of perpetual further sub-division. This exclusivity of proficiency will continue unless some way can be found to enhance average individual competence, and consequently there is a danger that fields will become not only exclusive but isolated, which would endanger the competence of the society as a whole. It is thus essential that there is movement between such areas by people who dabble in both while being proficient in neither, or combine proficiency in one with amateur competence in another. It is likely that liberal societies tolerate composite dilletantist professionalism of this kind, while status oriented and bureaucratic societies inhibit it, with obvious consequences.