No matter how thoroughly a person may have learned the Greek alphabet, he will never be in a condition to repeat it backwards without further trainin… - Hermann Ebbinghaus

Popular thought, supported by desires common to all human beings, readily accepts the view that mind is essentially different from matter, that its laws are in every respect different from the laws of material nature, and that the brain, being a part of the material nature, is simply the special tool used by the mind in its intercourse with nature.

Ideas which have been developed simultaneously or in immediate succession in the same mind mutually reproduce each other, and do this with greater ease in the direction of the original succession and with a certainty proportional to the frequency with which they were together.

Natural science served as - if we overlook the hasty identification of mind and matter which had its origin in natural science - as a shining and fruitful example to psychology.