Nothing is more practical than a good theory.

The life contest is primarily a competition for available energy.

It must be splendid to command millions of people in great national ventures, to lead a hundred thousand to victory in battle. But it seems to me greater still to discover fundamental truths in a very modest room with very modest means - truths that will still be foundations of human knowledge when the memory of these battles is painstakingly preserved only in the archives of the historian.

In my view all salvation for philosophy may be expected to come from Darwin's theory

Thermodynamics, correctly interpreted, does not just allow Darwinian evolution; it favors it.

The general struggle for existence of animate beings is not a struggle for raw materials, these for organisms are air water & soil, all abundantly available, nor for energy which exists in plenty in the sun and any hot body in the form of heat, but rather a struggle for entropy, which becomes available through the transition of energy from the hot sun to the cold earth.

Since a given system can never of its own accord go over into another equally probable state but into a more probable one, it is likewise impossible to construct a system of bodies that after traversing various states returns periodically to its original state, that is a perpetual motion machine.