Among the many things that made the Professor an excellent teacher was the fact that he wasn't afraid to say 'we don't know.' For the Professor, there was no shame in admitting you didn't have the answer, it was a necessary step toward the truth. It was as important to teach us about the unknown or the unknowable as it was to teach us what had already been safely proven.

— Yōko Ogawa

Because he had been- and in many ways still was-such a brilliant man, he no doubt understood the nature of his memory problem. It wasn't pride that prevented him from asking for help but a deep aversion to causing more trouble than necessary for those of us who lived in the normal world.

— Yōko Ogawa

Eternal truths are ultimately invisible, and you won't find them in material things or natural phenomena, or even in human emotions. Mathematics, however, can illuminate them, can give them expression - in fact, nothing can prevent it from doing so.

— Yōko Ogawa

For a torture to be effective, the pain has to be spread out; it has to come at regular intervals, with no end in sight. The water falls, drop after drop, like the second hand of a watch, carving uptime. The shock of each individual drop is insignificant, but the sensation is impossible to ignore. At first, one might manage to think about other things, but after five hours, after ten hours, it becomes unendurable. The repeated stimulation excites the nerves to a point where they literally explode, and every sensation in the body is absorbed into that one spot on the forehead---indeed, you come to feel that you are nothing but a forehead, into which a fine needle is being forced millimeter by millimeter. You can’t sleep or even speak, hypnotized by a suffering that is greater than any mere pain. In general, the victim goes mad before a day has passed.

— Yōko Ogawa

He preferred smart questions to smart answers.

— Yōko Ogawa

His ironing seemed highly rational, with a constant speed that allowed him to get the best results, with the least effort; all the economy and elegance of his mathematical proofs performed right there on the ironing board. The Professor was definitely the best man for this job, we had to admit, since the tablecloth was made of delicate lace.

— Yōko Ogawa

I couldn't reach him from here even if I tried.

— Yōko Ogawa

It was as if a tiny crack had opened somewhere in him and was growing, tearing him to pieces. If he had simply been angry, I might have found a way to calm him, but I had no idea how to put him back together once he came apart.

— Yōko Ogawa

It was clear that he didn't remember me from one day to the next. The note clipped to his sleeve simply informed him that it was not our first meeting, but it could not bring back the memory of the time we had spent together.

— Yōko Ogawa

I was impressed by the delicate weaving of the numbers. No matter how carefully you unraveled a thread, a single moment of inattention could leave you stranded, with no clue what to do next. In all his years of study, the Professor had managed to glimpse several pieces of the lace. I could only hope that some part of him remembered the exquisite pattern.

— Yōko Ogawa