All our thoughts and concepts are called up by sense-experiences and have a meaning only in reference to these sense-experiences. On the other hand, however, they are products of the spontaneous activity of our minds; they are thus in no wise logical consequences of the contents of these sense-experiences. If, therefore, we wish to grasp the essence of a complex of abstract notions we must for the one part investigate the mutual relationships between the concepts and the assertions made about them; for the other, we must investigate how they are related to the experiences.

The very same brain centers that interpret and feel physical pain also become activated during experiences of emotional rejection. In brain scans, they light up in response to social ostracism, just as they would when triggered by physically harmful stimuli. When people speak of feeling hurt or of having emotional pain, they are not being abstract or poetic, but scientifically quite precise.

Blue has no dimensions, it is beyond dimensions, whereas the other colours are not….All colours arouse specific associative ideas, psychologically material or tangible, while blue suggests at most the sea and sky, and they, after all, are in actual, visible nature what is most abstract.

Philosophy is not in a state of external reflection on other domains, but in a state of active and internal alliance with them, and it is neither more abstract nor more difficult.

No cause, no God, no abstract idea can justify the mass slaughter of innocents.

There’s a tiredness of abstract inteligence, and it’s the most horrible of tirednesses. It doesn’t weight on you like the tiredness of the body, nor does it worry you like the tiredness of knowledge and emotion. It’s a weightiness of the conscience of the world, an inability of the soul to breathe.