In mathematical quarters, the regular division of the plane has been considered theoretically. ... [Mathematicians] have opened the gate leading to an extensive domain, but they have not entered this domain themselves. By their very nature they are more interested in the way in which the gate is opened than in the garden lying behind it.

Are you really sure that a floor can't also be a ceiling?

It has always irked me as improper that there are still so many people for whom the sky is no more than a mass of random points of light. I do not see why we should recognize a house, a tree, or a flower here below and not, for example, the red Arcturus up there in the heavens as it hangs from its constellation Bootes, like a basket hanging from a balloon.

The regular division of the plane into congruent figures evoking an association in the observer with a familiar natural object is one of these hobbies or problems...I have embarked on this geometric problem again and again over the years, trying to throw light on different aspects each time. I cannot imagine what my life would be like if this problem had never occurred to me; one might say that I am head over heels in love with it, and I still don't know why.

He who wonders discovers that this in itself is wonder.

As far as I know, there is no proof whatever of the existence of an objective reality apart from our senses, and I do not see why we should accept the outside world as such solely by virtue of our senses.

I don't use drugs, my dreams are frightening enough.