In this paper the authors give a survey of biological phenomena , for which the term ‘differentiation’, used in the widest sense, has a meaningful application. The last chapter deals with some general aspects of differentiation and connected phenomena, such as polarity, symmetry, loss of potencies, dedifferentiation, redifferentiation, adifferentiation, regulation and integration.To prevent this article becoming too voluminous, the authors had to refrain from extending the treatment of differentiation to non-living matter and to human society.

The most important method of the experiential sciences is the so-called scientific induction, viz. the method that starts from the observation of the particular and individual and tends to obtain abstractly-general or universal statements. This article explains that such a progression from the individual to the universal can only be accounted for if it can be considered as an application of some general intellectual insights. As to the main feature, this application can be made explicit by means of the following (...) deductive syllogism : Maior : Whatever happens with regularity in the material world happens of necessity, i.e. by virtue of the proper nature of things. Minor : Now an investigation of the data of experience shows that a phenomenon of species A is regularly connected with a phenomenon of species B. Conclusion : Therefore, a phenomenon of species A is necessarily connected with a phenomenon of species B. The minor of this syllogism gives the result of the empirical research and this way of acting has to be accounted for by a critical investigation of the general methods used by physical science, the so-called methods of Stuart Mill . The foundation of the maior is given in section 4. It appears that this principle presupposes the absolute validity of the law of causality and, moreover, the determinism of the material nature. A few remarks are added concerning regularity and probability. The various individual instances which are the starting-point of scientific research are supposed to be the representatives of a certain species. This amounts to the supposition that there is a certain species-individual-structure in the material things. This problem is treated in section 5. In order to arrive at a general statement about a certain kind of phenomena it will usually be necessary to combine experiential data obtained at different times and places and in different individual circumstances. Such a procedure is based upon the general presupposition that nature is uniform. This general presuppositions implies in particular two presuppositions concerning the irrelevancy of time and place. These questions are dealt with in section 6. Finally in section 8 a few remarks are added concerning character and value of the general conclusions obtained by scientific induction. (shrink)