A world of atoms and void › Sensation and the Judgment Added to It

Book IV extends the bodily explanation to perception, mental images, and dreams. Its account of sight involves images or films issuing from objects. This is a proposed physical mechanism, and it should not be treated as established simply because the broader project seeks natural causes. An explanatory ambition and the correctness of a particular explanation are different achievements.

A more general distinction appears in Lucretius's discussion of misleading appearances. He separates what a sensory presentation supplies from an opinion the mind adds to it. In his argument, rejecting the senses altogether would remove the standard on which reasoning about appearances depends. That position is not equivalent to saying every quick interpretation of what we see is true.

For a contemporary illustration, suppose you read a short message and take it as hostile. The words on the screen and the intention you attribute to their sender are distinguishable. The interpretation may be justified, but it needs reasons beyond the fact that those words appeared. This analogy borrows the distinction between presentation and added judgment. It does not claim that Lucretius anticipated research on communication or proved a method for treating anxiety.