Drug discovery crude preparations are morphine, the active agent in opium, and digoxin, a heart stimulant originating from Digitalis lanata. Organic chemistry also led to the synthesis of many of the natural products isolated from biological sources. Historically, substances, whether crude extracts or purified chemicals, were screened for biological activity without knowledge of the biological target. Only after an active substance was identified was an effort made to identify the target. This approach is known as classical pharmacology, forward pharmacology, or phenotypic drug discovery. Later, small molecules were synthesized to specifically target a known physiological/pathological pathway, avoiding the mass screening of banks
Nothing comes from nothing Nothing comes from nothing Nothing comes from nothing () is a philosophical expression of a thesis first argued by Parmenides. It is associated with ancient Greek cosmology, such as is presented not just in the works of Homer and Hesiod, but also in virtually every internal system—there is no break in-between a world that did not exist and one that did, since it could not be created in the first place. The idea that "nothing comes from nothing", as articulated by Parmenides, first appears in his "Physics": The above, in a translation based on the John Burnet translation, appears as