It is not without cause that men feel the burden of their existence, though they are themselves the cause of those burdens. - Immanuel Kant

The whole interest of my reason, whether speculative or practical, is concentrated in the three following questions: What can I know? What should I do? What may I hope? (Critique of Pure Reason

Dare to know! Have the courage to use your own intelligence!

It is an empirical judgement [to say] that I perceive and judge an object with pleasure. But it is an a priori judgement [to say] that I find it beautiful, i.e. I attribute this satisfaction necessarily to every one.