The world of shapes, lines, curves, and solids is as varied as the world of numbers, and it is only our long-satisfied possession of Euclidean geometry that offers us the impression, or the illusion, that it has, that world, already been encompassed in a manageable intellectual structure. The lineaments of that structure are well known: as in the rest of life, something is given and something is gotten; but the logic behind those lineaments is apt to pass unnoticed, and it is the logic that controls the system.

At the beginning of the new millennium, we still do not know why mathematics is true and whether it is certain. But we know what we do not know in an immeasurably richer way than we did. And learning this has been a remarkable achievement-among the greatest and least-known of the modern era.

In the end, every scheme and every science is justified by itself or it is not justified at all.

More than sixty years ago, mathematical logicians, by defining precisely the concept of an algorithm, gave content to the ancient human idea of an effective calculation. Their definitions led to the creation of the digital computer, an interesting example of thought bending matter to its ends.

While science has nothing of value to say on the great and aching questions of life, death, love, and meaning, what the religious traditions of mankind have said forms a coherent body of thought... There is recompense for suffering. A principle beyond selfishness is at work in the cosmos. All will be well. I do not know whether any of this is true. I am certain that the scientific community does not know that it is false.

Arithmetic is where the content lies, and not logic; but logic prompts certainty, and not arithmetic.

The motion of the mind is conveyed along a cloud of meaning.~ There is this paradox that we get to meaning only when we strip the meaning from symbols.