For to obtain a pure and fundamental grasp of a man's physiognomy one must observe him when he is alone and left to himself. Any kind of society and conversation with another throw a reflection upon him which is not his own, mostly to his advantage; for he thereby is placed in a condition of action and reaction which exalts him. But, on the contrary, if he is alone and left to himself immersed in the depths of his own thoughts and sensations, it is only then that he is absolutely and wholly _himself_. And any one with a keen, penetrating eye for physiognomy can grasp the general character of his whole being at a glance. For on his face, regarded in and by itself, is indicated the ground tone of all his thoughts and efforts, the _arrêt irrevocable_ of his future, and of which he is only conscious when alone. 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.