Knowledge is empirical. Everything that we now know has been built on what has gone before. If we reach back far enough into ancient history what was knowledge then was as often as not the product of a fertile imagination, albeit probably of pure genius since only the learned and gifted in those days were literate. Albert Einstein once said, "I value my gift of imagination more than I value my gift for acquiring new knowledge." It is in the episteme of poets and philosophers of old that we find the beginnings of our own knowledge. An important one of these was an independent investigator of nature, a poet who lived just before the time of Christ.
Titus Lucretius Carus lived in Rome between 99 BC and 55 BC. He is famous for the only poem that he appears to have authored, titled "On the Nature of Things" (sometimes translated "On the Nature of the Universe"). Not much is known about his life but that he was probably patronized by one Gaius Memmius, a rogue Tribune known for rigging elections and making questionable deals. Lucretius was a zealous follower of Epicurus, the ancient Greek philosopher who taught that nothing should be believed except that which was tested through direct observation and logical deduction. Epicurus taught that the Universe was infinite and eternal, that the gods have no hand in the affairs of men but that the motions and interactions of atoms are the determinants of the world's events. Memmius is reported by Cicero to have owned the estate on which the ruins of Epicurus' house stood, and upon which he intended to build. It was probably this fact that sparked the relationship between Lucretius and Memmius, to whom his epic work is addressed.
Lucretius was not a scientist by any stretch of the imagination but he was a true master of the written word and a poet of substantial talent who through logical analysis hints often albeit unwittingly at the true nature of reality. Just as often as not, his interpretations border on the ludicrous.
In his remarkable work Lucretius fully describes the Brownian motion of atoms and explains clearly the Law of Conservation of Mass and Energy. He uses logic to conclude that atoms have a finite number of possible forms otherwise there would be atoms of infinite magnitude, but that the numbers of any one type of atom are infinite because the Universe is infinite. Atoms cannot combine indiscriminately otherwise monsters would arise, suggesting that there is order in this Universe after all, with some atoms fitting together with others and not with the rest. He also states that atoms have no color, even though he had no perception of the nature of electro-magnetic waves or of the fact that atoms are much smaller than the smallest wavelength of visible light. He rationalizes that the Earth is not the only world that exists otherwise all other matter and space are for naught. According to Lucretius, rot and decay gives rise to little worms, and in this way reveals how his understanding of the interplay of all atoms can produce the idea that spontaneous life can generate given the right conditions.
On the subject of the spirit Lucretius states that spirit and mind are one. Like Epicurus, he believes that there can be no life after death. There is no heaven and there is no hell. The gods did not create the world because the world has too many imperfections. He describes that when chopping a snake into smaller sections each section is seen to squirm therefore the spirit is also sectioned and so it follows that the spirit must dissipate upon death just like the mind dissipates.
Lucretius explains sight by stating that every object continually emits a very thin film that is a replica of its surface. We perceive distance by virtue of the air that is pushed before this film, the more air that is pushed and felt unconsciously by the eyes, the greater the distance that we perceive between the eye and the object. Lions cannot tolerate the sight of a crowing rooster, because the rooster's body contains atoms which when they get inside the lion's eyes, prick the eyeballs and cause acute pain. Because there are rough atoms and smooth atoms, the reflecting surface of a mirror allows the film to be bounced off cleanly and the image is perceived to be distant within the mirror because the amount of air times two is being pushed ahead of it. The difference of preference and tolerance with respect to a creature's preference for food proves that each have their own particular assemblage of atoms therefore one man's meat can be another's poison.
It is a puzzling thing however that Lucretius conceives of the possibility that the moon might be a sphere of which one half is illuminated, and that the sphere rotates, thereby showing growing and waning illuminating crescents, when in fact it is quite apparent through observation that one side of it always faces the Earth. It may be that his conclusion that looking too long at the sun can cause the eyes to burn from the seeds of fire that assault it through the direct rays therefrom is based on experience and that his own vision suffered as a result. The sun and moon are as large as they appear according to Lucretius. The seeds of fire are so potent and intense that it doesn't matter that the sun is so small.
To Lucretius, clouds are massive and give off thunderclaps when they collide or rub against one another. Water permeates all things, as can be seen by condensation and absorption. Clouds also absorb water until they burst and give forth rain. He concludes that clouds cannot be mist or air because then they would easily pass through each other, but rather that they are hard and breakable. They carry within them the seeds of fire, which give rise to lightning.
On the subjects of meteorology and geology he qualifies his explanations by saying that the possibilities are many. When we regard a corpse lying on the ground we must conclude any number of possibilities as to how the individual died, but that does not make him any less dead. He is not short of ideas on all those possibilities, but is certain of almost none.
Lucretius places himself occasionally above his forebears. He takes issue with Democratus'(c. 430-370 BC) theory that the limbs are held together by atoms of the body and mind arranged alternately, and instead perceives of the atoms of the mind as being far fewer in number and distributed disproportionately throughout the body. In doing so he unwittingly hints at the distributions of the neurons in the brain and those of the enteric system.
There are the occasional references in the poem to times in the world's history upon which we speculate even today. For example, he refers to the "Universal Deluge", attributing the non-stop rains of the diluvial period to the fact that atoms are amply supplied out of the infinite. There is a possible reference to the dinosaur, when he describes the early life forms that the earth originally brought forth. He writes of mutant monsters with limbs pulled close to their chests, deformed creatures with the tails of snakes, the bodies of goats, and the heads of lions, as one might describe the fierce beasts of prehistoric times.
Lucretius rejects the supplication and idolatry awarded to the gods that the practice might bestow some materialistic favor upon the worshiper, and concludes by saying that true piety lies in the power to contemplate the Universe with a quiet mind.
Lucretius did not lack imagination and was possessed of a fertile mind. He appears to be no less intelligent than most great thinkers of today, but was of course limited to working with the information that he had to work with. It must be concluded that some minds are gifted while the rest are not. It is not surprising then that even today the majority of people cannot do the calculus, many cannot even do fractions, but there were minds even predating Lucretius' who laid the groundwork for the method of integration, for example as found in the Egyptian Moscow papyrus (c. 1800 BC) or in Archimedes' (c. 287-212 BC) invention of heuristics which resemble integral calculus.
It is a fine yet sticky line that divides the imagination from the truth. It is from imagination that we sow the seeds of learning through deeper investigation and from learning that we acquire knowledge.