The psychologist must be a strict empiricist.

It's not the size of the dog in the fight, it's the size of the fight in the dog.

What we do inwardly will change outer reality.

As in geometry the most natural way of beginning is from a mathematical point, so is the same method in observations and natural history the most genuine, simple, and instructive.

【释义】弹弓打鸟，千金不如泥丸合适。【延伸】一件事有很多种解决办法，找到最合适的一种，才能在每件事上都事半功倍。最贵的，不一定是最合适的，最合适的一定是最好的。

释义：能不说的话就不必多说，走路时要谨慎慢行，不要随意乱走。