"Enlightenment is man's emergence from his self-imposed immaturity. Immaturity is the inability to use one's understanding without guidance from another. This immaturity is self-imposed not when its cause lies in lack of understanding, but in lack of resolve and courage to use it without guidance from another. Sapere Aude! ['Dare to know!'] 'Have courage to use your own understanding!' - that is the motto of enlightenment."
The rest of the essay or more or less a restatement of and expansion upon this sentiment; and what a sentiment it is. Just imagine what the film The Wizard of Oz would have been like if someone had shown the characters just this one paragraph at the start. The entire thing would've been filmed without the scarecrow, at the very least.
A latter part of the essay talks about the conditions under which widespread enlightenment could be attained; Kant says that, a) it would be a slow process and b) it could only be attained by granting people greater freedom. Essentially, the hands off approach, for a long time, with a healthy dose of hoping for the best.
With a nod and a wink at the French Revolution - which at the time of writing the essay (1784), hadn't even happened yet: he's that good - Kant tells us that autocratic despotism can be overthrown, but that still doesn't change the root cause of immaturity as he thinks of it. After all, killing your king and crowning a new one isn't the most fruitful of activities; enlightenment doesn't come from a new government, it comes from new ways of thinking, and more importantly, acting upon those thoughts. The stinking, foetid nappy of society cannot be cast hurriedly into bin bags of history; we are bound to emptying our own papsacks first, or nothing whatsoever will be achieved. Kant recognised this and also recognised that without a new way of thinking, the old prejudices that exist before a revolution will simply be reconfigured rather than removed, as maintaining the immature worldview en masse means maintaining more or less the same structure for society, and doesn't change individual outlooks. Immature individuals make for an immature society, in other words.
Kant (necessarily) views the idea of a group of persons dedicating themselves to a single unalterable set of ideas as absurd, and also says that if these people are among those who at present act as the intellectual guardians of others, then their actions necessarily thwart enlightenment, as they deny people the opportunity to use their own reason. The example given (and by far the easiest to think of) is of the religious, in particular Christianity, but by no means is dogma restricted to one faith or ideology. Almost all other religions and a fair few ideologies make the same mistake; one non-religious group which does this would be Marxists, who seem to be not all that different in structure to a religion; sectarian divides over doctrine, theorists who are only usually ever questioned by other theorists, and the near hero worship of the ideology's progenitor himself. Members of the vanguard, or pastors of the Church of Marx? It can be hard to tell.
As coincidence would have it, there is one religion that seems to be tolerant of multiple doctrines so long as they are, at heart, compatible. Buddhism; yes, Buddhism. The other folks who talk about enlightenment a lot; admittedly in a different sense, but there are similarities. The Buddha himself also apparently said that his own means of becoming enlightened was not necessarily the only one; similarity ensues, as this does seem to imply that if one has the courage to use their reason, one can find enlightenment in a different way. A little uncanny, but I digress.
Towards the end Kant asks, "Do we live in an enlightened age?", and answers "no, but we do live in an age of enlightenment." For the benefit of the slow, this means that when Kant wrote his essay, he believed that although still relatively unenlightened, progress was being made. From today's perspective it seems not. Although it should be noted religious freedom has increased, and that the essay was at least in part devoted to promoting it (among many other intellectual freedoms*), it doesn't seem that many people utilise this freedom, as rather than having their reason subdued by the state, many of those who are religious would likely to held to account by compatriots of their own faith if they were to question or convert. Many more would have their freedom respected, but it seems there are still a few hangers on who think they have a duty to impose upon others. (May many doors be shut in their faces as they hand out their pamphlets. Also, note for preachers: hellfire and damnation only sell to the very very stupid. Try something more amicable.)
The moral defensibility of imposing yourself upon others has, fortunately, passed. Any remotely right thinking person can see that so long as no harm is done to others, anything goes. This doesn't necessarily mean that "anything" is desirible, but Kant, among others, realised that without the freedom to consider different courses of action, people are less human; it could even be argued that a person whose actions are dictated by fear of punishment is amoral. Thanks to the freedom of speech that wouldn't exist if dogmatic doctrines had won the day, we can say all of this; or in other words, thanks to freedom, we can use our reason without fear.
So, the short version of what Kant said? Be brave when you use your brain, because the worst thing you can be is wrong. At some point along the course of writing this, I will probably be very wrong. But I will be wrong because of what I've tried, not because of what I've neglected to try.
