As the reactions become more fixed they develop into longer and more complicated series, which then appear to us as _instinctive actions_. But here, too, we find the characteristic unsuitability when unwonted circumstances arise, even if the teleologic reactions to stimuli become more manifold. Finally, there are the _conscious acts_ which appear to us to be the highest degree of the series. It is with the teleologic regulation of these conscious acts, including the very highest activities of mankind, that this book deals. They are distinguished from instinctive action by the fact that they no longer proceed in a single and definite series, but are combined at need in the most manifold ways. But the fundamental fact, namely, that actions are based upon the repetition of coinciding experiences, at once appears here also, since the basis of the entire conscious life of the soul, the formation of _concepts_, is made possible only through _repetition_. Thus, we are justified in regarding the various degrees of mental activity from the simplest reflex manifestation to the highest mental act as a connected series of increasingly manifold and purposive actions proceeding from the same physico-chemical and physiological foundation. =57. Feeling, Thinking, Acting.= For good reasons it is generally assumed that the organisms have not always been what they are now, but have "developed" from previous simpler forms. It is undecided whether originally there were one or several forms from which the present forms sprang, nor is it known how life first made its appearance on earth. So long as the various assumptions with regard to this question have not led to decisive, actually demonstrable differences in the results, a discussion of it is fruitless, and therefore unscientific. The usual word evolution is non-purposive in so far as it signifies the appearance of something already existing. Another conception is better according to which the influence of _changed_ conditions of existence has yielded the most important factor of change. The change that the organisms undergo is always in a definite direction. More and more complex and manifold forms are evolved, and the evolution of these forms is characterized by an ever greater specialization of the functions of life, so that every specially developed organ comes to perform but one function. It is true that by this means the organism is better fitted to perform those functions, but at the same time it grows more susceptible to injury, since its existence depends upon the proper simultaneous activity of many different organs. Such an evolution, therefore, can occur only when the general conditions of life have grown steadier, so that the danger of disturbance becomes less. We are accustomed to regard changes in this direction as higher developments, and the progressive simplifications of the organization (as for example in parasites) as backward steps.