Travelling, whether in the mental or the physical world, is a joy, and it is good to know that, in the mental world at least, there are vast countries still very imperfectly explored

The faculty of being acquainted with things other than itself is the main characteristic of a mind.

When two things have frequently existed in close temporal contiguity, either comes in time to cause the other.

Liberation from the tyranny of the body contributes to greatness, but just as much to greatness in sin as to greatness in virtue.

To the primitive mind, everything is either friendly or hostile; but experience has shown that friendliness and hostility are not the conceptions by which the world is to be understood.

In attempting to understand the elements out of which mental phenomena are compounded, it is of the greatest importance to remember that from the protozoa to man there is nowhere a very wide gap either in structure or in behaviour. From this fact it is a highly probable inference that there is also nowhere a very wide mental gap.