The test of real and vigorous thinking, the thinking which ascertains truths instead of dreaming dreams, is successful application to practice.
John Stuart MillThe ends of scientific classification are best answered, when the objects are formed into groups respecting which a greater number of general propositions can be made, and those propositions more important, than could be made respecting any other groups into which the same things could be distributed. ... A classification thus formed is properly scientific or philosophical, and is commonly called a Natural, in contradistinction to a Technical or Artificial, classification or arrangement.
John Stuart MillHe who lets the world, or his own portion of it, choose his plan of life for him, has no need of any other faculty than the ape-like one of imitation. He who chooses his plan for himself, employs all his faculties. He must use observation to see, reasoning and judgment to foresee, activity to gather materials for decision, discrimination to decide, and when he has decided, firmness and self-control to hold to his deliberate decision.
John Stuart MillIf it were only that people have diversities of taste, that is reason enough for not attempting to shape them all after one model. But different persons also require different conditions for their spiritual development, and can no more exist healthily in the same moral, than all the varieties of plants can in the same physical, atmosphere and climate.
John Stuart Mill