O ptimists have been telling doom-mongers to cheer up since at least 1710, when the philosopher Gottfried Leibniz concluded that ours must be the best of all possible worlds, on the grounds that God, being perfect and merciful, would hardly have created one of the more mediocre ones instead. But the most recent outbreak of positivity may be best understood as a reaction to the pessimism triggered by the terrorist attacks of 11 September 2001. For one thing, those attacks were a textbook example of the kind of high-visibility bad news that activates our cognitive biases, convincing us that the world is becoming lethally dangerous when really it isn’t: in reality, a slightly higher number of Americans were killed while riding motorcycles in 2001 than died in the World Trade Center and on the hijacked planes.
Locke attacks both the view that we have any innate principles (for example, the whole is greater than the part, do unto others as you would have done unto you, etc.) as well as the view that there are any innate singular ideas (for example, God, identity, substance, and so forth). The main thrust of Locke’s argument lies in pointing out that none of the mental content alleged to be innate is universally shared by all humans. He notes that children and the mentally disabled, for example, do not have in their minds an allegedly innate complex thought like “equals taken from equals leave equals”. He also uses evidence from travel literature to point out that many non-Europeans deny what were taken to be innate moral maxims and that some groups even lack the idea of a God. Locke takes the fact that not all humans have these ideas as evidence that they were not implanted by God in humans minds, and that they are therefore acquired rather than innate.