The constant flux and caprice of mental events do not admit of the establishment of stable experimental conditions.
Hermann Ebbinghaus

The desire to economize time and mental effort in arithmetical computations, and to eliminate human liability to error is probably as old as the science of arithmetic itself.
Howard Aiken

The difference between a healthy person and one who is mentally ill is the fact that the healthy one has all the mental illnesses, and the mentally ill person has only one.
Robert Musil

The difference between winning and losing is always a mental one.
Peter Thomson

The final upshot of thinking is the exercise of volition, and of this thought no longer forms a part; but belief is only a stadium of mental action, an effect upon our nature due to thought, which will influence future thinking.
Charles Sanders Peirce

The first four months of writing the book, my mental image is scratching with my hands through granite. My other image is pushing a train up the mountain, and it's icy, and I'm in bare feet.
Mary Higgins Clark

The first requisite for success is the ability to apply your physical and mental energies to one problem incessantly without growing weary.
Charles Caleb Colton

The fundamentalists have taken the fun out of the mental.
Ken Kesey

The general statement that the mental faculties are class concepts, belonging to descriptive psychology, relieves us of the necessity of discussing them and their significance at the present stage of our inquiry.
Wilhelm Wundt

The habit of common and continuous speech is a symptom of mental deficiency. It proceeds from not knowing what is going on in other people's minds.
Walter Bagehot

The higher mental development of woman, the less possible it is for her to meet a congenial male who will see in her, not only sex, but also the human being, the friend, the comrade and strong individuality, who cannot and ought not lose a single trait of her character.
Emma Goldman

The key to success is to keep growing in all areas of life - mental, emotional, spiritual, as well as physical.
Julius Erving

The making of an Atheist implies a mental stimulation and training which brings into play the primary factors of social progress.
Joseph McCabe

The mental act of sensation which issues in reflex movement is so simple as to defy analysis.
Samuel Alexander

The only antidote to mental suffering is physical pain.
Karl Marx

The pain was considerable, but trivial compared with my mental state.
Harold Lloyd

The path of least resistance and least trouble is a mental rut already made. It requires troublesome work to undertake the alternation of old beliefs.
John Dewey

The pool is terrible, but that doesn't have much to do with my record swims. That's all mental attitude.
Mark Spitz

The product of mental labor - science - always stands far below its value, because the labor-time necessary to reproduce it has no relation at all to the labor-time required for its original production.
Karl Marx

The results of ethnic psychology constitute, at the same time, our chief source of information regarding the general psychology of the complex mental processes.
Wilhelm Wundt