Spencer, H. (1880). The instability of the homogeneous. In H. Spencer, World's famous literature. First principles (pp. 337-362). Philadelphia, PA, US: David McKay Publisher.
http://dx.doi.org/10.1037/12424-024
The difficulty of dealing with transformations so many-sided as those which all existences have undergone, or are undergoing, is such as to make a definite or complete deductive interpretation seem almost hopeless. So to grasp the total process of redistribution of matter and motion as to see simultaneously its several necessary results in their actual interdependence, is scarcely possible. There is, however, a mode of rendering the process as a whole tolerably comprehensible. Though the genesis of the rearrangement undergone by every evolving aggregate is in itself one, it presents to our intelligence several factors; and after interpreting the effects of each separately, we may, by synthesis of the interpretations, form an adequate conception. On setting out, the proposition which comes first in logical order is, that some rearrangement must result; and this proposition may be best dealt with under the more specific shape, that the condition of homogeneity is a condition of unstable equilibrium. The general principle, now to be followed out in its applications, is thus somewhat more comprehensive than the title of the chapter implies. No demurrer to the conclusions drawn can be based on the ground that perfect homogeneity nowhere exists; since, whether that state with which we commence be or be not one of perfect homogeneity, the process must equally be toward a relative heterogeneity. (PsycINFO Database Record (c) 2016 APA, all rights reserved)