In Book Four of On the Nature of Things Lucretius first explores sensation. Here some of his ideas sound more silly than prescient, especially his idea that objects put off tiny particles that are a film containing and image and that it is the contact with that film which causes sight. Blurry images are the result of the film running into stuff and getting worn down as it travels from the object to the eye. This entire section revealed the limitations of a strict materialism. When Newton developed his views on gravity and optics it upset earlier scientific views which were more strictly materialist.
Much like Dr. Johnson or G. E.-this-is-a-hand-Moore, Lucretius gives a pretty direct and simple refutation of a full skepticism -- the very concept of truth has arisen from the senses and you can't find any authority to trust more than the senses. If you followed skepticism, your entire life would fall apart. This also is a good pre-pragmatic argument.
I mostly skimmed his treatment of the other physical senses, but his section on love, orgasm, and sex is quite enjoyable. It's funny in some places and a little hot in others.
Explaining attraction -- "The goaded regions swell with seed, and then/ Comes the delight to dart the same at what/ The mad desire so yearns."
Erotic desire is a form of madness in which we attempt to consume one another and cannot be satiated because we cannot achieve this end. There is a violence in delight. Better, he thinks, not to fall in love and avoid the thing.
He suggests that one is more like to impregnate a woman in doggy style, his term is "in manner of wild-beasts,/ After the custom of four-foot breeds." He thinks if a woman is took active and enjoys the sex too much, that she is less likely to get pregnant. This is the strategy prostitutes use, he writes, trying to please the man, which is something "Our wives have never need of."
Books V and VI to go, and then this week I purchased Stephen Greenblatt's award-winning book The Swerve, which explores the influence of Lucretius' On the Nature of Things. I'll read it before moving along to Marcus Aurelius' Meditations.