A Commonplace Book

With many a science the endeavor to discover a universal principle is perhaps often just as fruitless as would be the endeavor of a mineralogist to discover a primal universal substance out of which all the minerals had arisen. Nature creates, not genera and species, but individua, and our shortsightedness has to seek out similarities so as to be able to retain in mind many things at the same time. These conceptions become more and more inaccurate the larger the families we invent for ourselves.

We call people mad when the regulation of their conceptions no longer corresponds to the sequence of events in our regular world; for which reason a careful observation of nature, or of mathematics, is certainly the most effective specific against madness...

It is a general source of misfortune to us that we believe things are in actuality what they in fact only signify.

The common individual always conforms to the prevailing opinion and the prevailing fashion; he regards the state in which every thing now exists as the only possible one and passively accepts it all. It does not occur to him that everything, from the shape of the furniture up to the subtlest hypothesis, is decided by the great council of mankind of which he is a member.

The most successful tempters and thus the most dangerous are the deluded deluders.

A great speech is easy to learn by heart and a great poem even easier. How hard it would be to memorize as many words linked together senselessly, or a speech in a foreign tongue! Sense and understanding thus come to the aid of memory. Sense is order and order is in the last resort conformity with our nature. When we speak rationally we are only speaking in accordance with the nature of our being. That is why to annex something to our memory we always seek to introduce sense or some other kind of order into it. That is why we devise genera and species in the case of plants and animals. The hypotheses we make belong here too: we are obliged to have them because otherwise we would be unable to retain things... The question is, however, whether everything is legible to us. Certainly experiment and reflection enable us to introduce a significance into what is not legible, either to us or at all: thus we see faces or landscapes in the sand, though they are certainly not there. The introduction of symmetries belongs here too, silhouettes in inkblots, etc. Likewise the gradation we establish in the order of creatures: all this is not in the things but in us. In general we cannot remember too often that when we observe nature, and especially the ordering of nature, it is always our selves alone we are observing.