Even if all parts of a problem seem to fit together like the pieces of a jigsaw puzzle, one has to remember that the probable need not necessarily be the truth and the truth not always probable.

The dream is the liberation of the spirit from the pressure of external nature, a detachment of the soul from the fetters of matter.

Thinking is an experimental dealing with small quantities of energy, just as a general moves miniature figures over a map before setting his troops in action.

Anxiety in children is originally nothing other than an expression of the fact they are feeling the loss of the person they love.

The first requisite of civilization, therefore, is that of justice — that is, the assurance that a law once made will not be broken in favour of an individual. This implies nothing as to the ethical value of such a law.

It must be pointed out, however, that strictly speaking it is incorrect to talk of the dominance of the pleasure principle over the course of mental processes. If such a dominance existed, the immense majority of our mental processes would have to be accompanied by pleasure or to lead to pleasure, whereas universal experience completely contradicts any such conclusion.

The adoption of the required attitude of mind towards ideas that seem to emerge "of their own free will" and the abandonment of the critical function that is normally in operation against them seem to be hard of achievement for some people. The "involuntary thoughts" are liable to release a most violent resistance, which seeks to prevent their emergence. If we may trust that great poet and philosopher Friedrich Schiller, however, poetic creation must demand an exactly similar attitude.