First Principles (Barnes & Noble Digital Library‪)‬

 One of the author’s many treatises on the foundations of knowledge, this collection focuses on science. Part One, “The Unknowable,” discusses ultimate religious and scientific theories which Spencer sees as unknowable. Part Two, “The Knowable,” explains data; concepts such as motion, forces, and evolution; segregation; equilibrium; and dissolution—in other words, concepts that are provable and knowable.