There is a true and a false philosophy. As froth in new-made wine swims upon the top and hides the true wine below, likewise there is a froth of sophistry and pseudo-philosophy swimming at the top of true philosophy; it looks like knowledge, but it is the outcome of ignorance, gilded and varnished to deceive the vulgar. It is like a parasite growing upon the tree of knowledge, drawing the sap out of the true tree and converting it into poison. The intellectual working of the brain alone is not sufficient to give birth to a physician; the true physician is not he who has merely heard of the truth, but he who feels the truth, who sees it before him as clearly as the light of the sun, who hears it as he would hear the noise of the cataract of the Rhine or the whistling of the storm upon the ocean, who smells it and tastes it, it being sweet to him as honey or bitter as gall. Nature produces diseases and effects their cures, and where, then, could be found a better teacher than Nature herself? That alone which we see and feel and perceive constitutes true knowledge, not that of which we are merely informed in books and which is not confirmed by experience.

The knowledge of Nature as it is--not as we imagine it to be--constitutes true philosophy. He who merely sees the external appearance of things is not a philosopher; the true philosopher sees the reality, not merely the outward appearance. He who knows the sun and the moon has a sun and a moon in him, and he can tell how they look, even if his eyes are shut. Thus the true physician sees in himself the whole constitution of the Microcosm of man, with all its parts. He sees the constitution of his patient as if the latter were a clear crystal, in which not even a single hair could escape detection. He sees him as he would the stones and pebbles at the bottom of a clear well. This is the philosophy upon which the true art of medicine is based. Not that your physical eyes are able to show you these things, but it is Nature herself who teaches it to you. Nature is the universal mother of all, and if you are in harmony with her--if the mirror of your mind has not been made blind by the cobwebs of speculations, misconceptions, and erroneous theories--she will hold up before you a mirror in which you will see the truth. But he who is not true himself will not see the truth as it is taught by Nature, and it is far easier to study a number of books and to learn by heart a number of scientific theories than to enoble one's own character to such an extent as to enter into perfect harmony with Nature and to be able to see the truth.

Paracelcus, 16th century Swiss physician and alchemist