Lucretius

Titus Lucretius Carus, often shortened to Lucretius in an attempt to sound casual, was a Roman philosopher who spent his life trying to popularize the ideas of Epicurus in the Roman world. His one surviving work, De Rerum Natura (On The Nature of Things), besides being very good bedtime reading, represents an early attempt to work out the structure of the universe using reason.

Views on death
In his massive poem De Rerum Natura Lucretius wrote lots of fancy words in order to draw Romans to Epicureanism since Epicurus was only really famous in Greece at the time. In the poem/book, Lucretius takes on the task of persuading people that they should not fear death. Death is somewhat worrying for most people, but an attempt to tackle fear of it philosophically is rare.

Lucretius' philosophy of death is often called the Symmetry Argument and goes as follows:


 * In the time before your birth, you did not exist
 * In the time after your death, you will not exist
 * The existence in both cases is the same
 * Because you don't suffer in the time before you're born, you will not suffer in the time after your death
 * So it doesn't make sense to fear your death

He expresses the idea a little more poetically as follows: Look back now and consider how the bygone ages of eternity that elapsed before our birth were nothing to us. Here, then, is a mirror in which nature shows us the time to come after our death. Do you see anything fearful in it? Do you perceive anything grim? Does it not appear more peaceful than the deepest sleep?

Where he was wrong
Almost everything. This is understandable since he (and his society) had the scientific knowledge of a dead whelk. However, even the ideas which were utterly wrong are often amusing and represent a heartening attempt at a rational view of nature in an age that Lucretius saw as one of superstition. For instance, he believed that thunder was caused by clouds being spun into balloons by the wind and then popping, that fire exists in particulate form inside all things and can sometimes be knocked out to create sparks, and that there could be no fundamental force of gravity because then trees would not be able to get water up off the ground without lifting it (you can't really blame him for not knowing about transpiration and capillary action). Sadly, one area where he and other Epicureans promulgated the wrong opinion other intellectuals of the day actually got right is believing the earth was flat, plus that the sun is much smaller than its true size.

Where he was right
He came up with something uncannily similar to the theory of evolution by natural selection a couple of thousand years ahead of time. Mention of this is often neglected, and it remains unclear how much (if any) impact it had on later science. He also is the first person to describe Brownian motion (in the example of dust particles) and used it as proof that atoms existed. Of course, the existence of atoms is itself something he got right (though things are far more complicated in modern physics), but this predates him by centuries.

He also believed the universe was infinite and provided a logical proof in De Rerum Natura: Stand at the edge of the universe and shoot an arrow. The arrow either goes on forever, or it hits a wall - so stand on that wall and shoot again. You can keep doing that infinitely. There are only the same two possible outcomes. Therefore, the universe is infinite. It wouldn't be considered scientific these days, but it was good enough back then, and it proved a big inspiration to Giordano Bruno, who got burned at the stake in 1600 for believing such un-Catholic things. Bruno's story, including a delightful animated version of Lucretius' thought experiment, is told in Neil DeGrasse Tyson's Cosmos reboot.

Richard Carrier has pointed out that if Lucretius' poem were interpreted like religious apologists do with respect to their sacred books on supposed prophetic predictions of scientific facts (see Biblical scientific errors and Qur'anic scientific foreknowledge), Lucretius predicts a larger number of them (and more rationaly justifed), such as: the existence of the atom (I.265-328), the law of inertia (II.62-166, II.184-332), photons (II.144-156), the theory of evolution (II.1150-1156, V.790-836), the theory of relativity (I.459-463, II.308-332), quantum indeterminism (II.216-293) and Brownian motion (II.112-141).