Mechanicism does not constitute a single set of ideas, for it can present itself through several perspectives. Biological thinking from the nineteenth century constitutes a good example of the diversity of mechanistic approaches. Thus, investigations in which the study of biological theories is based on generic concepts should be avoided: each theory should be understood in terms of its own conceptual fabric. The German biologist Ernst Haeckel elaborates a monist philosophy by means of a physical-chemical mechanicism in which the vital processes are special cases of universal laws. The construction of this philosophy involves a criticism of the traditional contact-based mechanicism. The German philosopher Friedrich Nietzsche, based on Wilhelm Roux's neo-Lamarckist mechanics of development, develops an explanation of life that dispenses both with mechanicism and with teleological conceptions, namely, the struggle of impulses or forces for more power (will to power). Such examples show the interdependence between science and philosophy in nineteenth century biology, and the importance of studying the thought of the authors who took part in this historical process.
Mechanicism; Biology; Haeckel; Nietzsche; Roux; Monism; Criticism of metaphysics; Mechanics of development