Talking about knowable things in this chapter, the auther expounds the evolutionary points of view of in this phenomenal world. He finally draws the conclusion: the deepest truth available is the profound, heterogeneo and simple statements that we get by experiencing for the relation between materials, movement and force. Those are merely symbols of "the unknown reality". The essence is always an uncomprehending force, and we can never imagine what consequences its force within time limits or space boundaries will bring to us.

In the First principles (II), Spencer, encouraged by the philosophy theory of the split of noumenon and phenomenon, holds that social phenomena, including material, motion, space, time, etc. and these concepts are relative. For example, the material can be infinitely divisible, and it can also be made up of indivisible particles. There is an unknowable reality behind this paradox, that is, the reality of force. The phenomenon is determined by an unknowable reality. In view of the "the permanence of force", he thinks that evolution is the condensation of substances accompanied by their dissipation, and those substances evolve from unfixed homogeneity to a fixed convergence of heterogeneous condition, and then back to the original. This evolutional state is presented by the promotion of force under the real state. Dissipation and coagulation achieve a complete equilibrium in the end, but equilibrium begins to move in the process of dispersion later.

Herbert Spencer (27 April 1820 – 8 December 1903) was an English philosopher, biologist, anthropologist, sociologist, and prominent classical liberal political theorist of the Victorian era.Spencer developed an all-embracing conception of evolution as the progressive development of the physical world, biological organisms, the human mind, and human culture and societies.