Justus von Liebig - Collected Quotes

"The loveliest theories are being overthrown by these damned experiments; it's no fun being a chemist anymore." (Justus von Liebig, [letter to Berzelius] 1834)

"But a thousand unconnected observations have no more value, as a demonstrative proof, than a single one. If we do not succeed in discovering causes by our researches, we have no right to create them by the imagination; we must not allow mere fancy to proceed beyond the bounds of our knowledge." (Justus von Liebig, "The Lancet", 1844)

"Observation is like a piece of glass, which, as a mirror, must be very smooth, and must be very carefully polished, in order that it may reflect the image pure and undistorted." (Justus von Liebig, "The Study of the Natural Sciences", 1853) 

"The person who observes a clock, sees in it not only the pendulum swinging to and fro, and the dial-plate, and the hands moving, for a child can see all this; but he sees also the parts of the clock, and in what connexion the suspended weight stands to the wheel-work, and the pendulum to the moving hands." (Justus von Liebig, "The Study of the Natural Sciences", 1853) 

"There is no art so difficult as the art of observation: it requires a skillful, sober spirit and a well-trained experience, which can only be acquired by practice; for he is not an observer who only sees the thing before him with his eyes, but he who sees of what parts the thing consists, and in what connexion the parts stand to the whole." (Justus von Liebig, "The Study of the Natural Sciences", 1853) 

"When the observer has ascertained the foundation of a phenomenon, and he is able to associate its conditions, he then proves while he endeavours to produce the phenomena at his will, the correctness of his observations by experiment. To make a series of experiments is often to decompose an opinion into its individual parts, and to prove it by a sensible phenomenon. The naturalist makes experiments in order to exhibit a phenomenon in all its different parts. When he is able to show of a series of phenomena, that they are all operations of the same cause, he arrives at a simple expression of their significance, which, in this case, is called a Law of Nature. We speak of a simple property as a Law of Nature when it serves for the explanation of one or more natural phenomena." (Justus von Liebig, "The Study of the Natural Sciences", 1853)

"When a power of nature, invisible and impalpable, is the subject of scientific inquiry, it is necessary, if we would comprehend its essence and properties, to study its manifestations and effects. For this purpose simple observation is insufficient, since error always lies on the surface, whilst truth must be sought in deeper regions." (Justus von Liebig, "Familiar Letters on Chemistry", 1859)

"The progress of mankind is due exclusively to the progress of natural sciences, not to morals, religion or philosophy." (Justus von Liebig, [Letter to Schoenbein] 1866) 

"There is in the chemist a form of thought by which all ideas become visible in the mind as strains of an imagined piece of music." (Justus von Liebig)