I have endeavoured to show that no absolute structural line of demarcation, wider than that between the animals which immediately succeed us in the scale, can be drawn between the animal world and ourselves; and I may add the expression of my belief that the attempt to draw a physical distinction is equally futile, and that even the highest faculties of feeling and of intellect begin to germinate in lower forms of life.

The ultimate court of appeal is observation and experiment... not authority.

Our reverence for the nobility of manhood will not be lessened by the knowledge that man is in substance and in structure, one with the brutes; for he alone possesses the marvellous endowment of intelligible and rational speech whereby he has slowly accumulated and organized the experience which is almost wholly lost with the cessation of individual life in other animals; so that he now stands raised above it as on a mountain-top, far above the level of his humble fellows, and transfigured from his grosser nature by reflecting, here and there, a ray from the infinite source of truth.

If the hypothesis of evolution is true, living matter must have arisen from non-living matter; for by the hypothesis the condition of the globe was at one time such, that living matter could not have existed in it, life being entirely incompatible with the gaseous state.

I really see no harm which can come of giving our children a little knowledge of physiology. ... The instruction must be real, based upon observation, eked out by good explanatory diagrams and models, and conveyed by a teacher whose own knowledge has been acquired by a study of the facts; and not the mere catechismal parrot-work which too often usurps the place of elementary teaching.

Ecclesiasticism in science is only unfaithfulness to truth

I cannot but think that he who finds a certain proportion of pain and evil inseparably woven up in the life of the very worms, will bear his own share with more courage and submission.