The science of physiognomy is one of the principal means of a knowledge of mankind:  arts of dissimulation do not come within the range of physiognomy, but within that of mere pathognomy and mimicry.  This is precisely why I recommend the physiognomy of a man to be studied when he is alone and left to his own thoughts, and before he has been conversed with; partly because it is only then that his physiognomy can be seen purely and simply, since in conversation pathognomy immediately steps in, and he then resorts to the arts of dissimulation which he has acquired; and partly because personal intercourse, even of the slightest nature, makes us prejudiced, and in consequence impairs our judgment.

Concerning our physiognomy in general, it is still to be observed that it is much easier to discover the intellectual capacities of a man than his moral character.  The intellectual capacities take a much more outward direction.  They are expressed not only in the face and play of his features, but also in his walk, nay, in every movement, however slight it may be.  One could perhaps discriminate from behind between a blockhead, a fool, and a man of genius.  A clumsy awkwardness characterises every movement of the blockhead; folly imprints its mark on every gesture, and so do genius and a reflective nature.  Hence the outcome of La Bruyere’s remark:  Il n’y a rien de si delie, de si simple, et de si imperceptible ou il n’y entrent des manieres, qui nous decelent:  un sot ni n’entre, ni ne sort, ni ne s’assied, ni ne se leve, ni ne se tait, ni n’est sur ses jambes, comme un homme d’esprit.  This accounts for, by the way, that instinct stir et prompt which, according to Helvetius, ordinary people have of recognising people of genius and of running away from them.  This is to be accounted for by the fact that the larger and more developed the brain, and the thinner, in relation to it, the spine and nerves, the greater not only is the intelligence, but also at the same time the mobility and pliancy of all the limbs; because they are controlled more immediately and decisively by the brain; consequently everything depends more on a single thread, every movement of which precisely expresses its purpose.  The whole matter is analogous to, nay dependent on, the fact that the higher an animal stands in the scale of development, the easier can it be killed by wounding it in a single place.  Take, for instance, batrachia:  they are as heavy, clumsy, and slow in their movements as they are unintelligent, and at the same time extremely tenacious of life.  This is explained by the fact that with a little brain they have a very thick spine and nerves.  But gait and movement of the arms are for the most part functions of the brain; because the limbs receive their motion, and even the slightest modification of it, from the brain through the medium of the spinal nerves; and this is precisely why voluntary movements tire us.  This feeling of fatigue, like