“The light dove, in free flight cutting through the air the resistance of which it feels, could get the idea that it could do even better in airless space. Likewise, Plato abandoned the world of the senses because it posed so many hindrances for the understanding, and dared to go beyond it on the wings of the ideas, in the empty space of pure understanding.”

“The schematicism by which our understanding deals with the phenomenal world ... is a skill so deeply hidden in the human soul that we shall hardly guess the secret trick that Nature here employs.”

“Space and time are the framework within which the mind is constrained to construct its experience of reality.”

“Enlightenment is man's exodus from his self-incurred tutelage. Tutelage is the inability to use one's understanding without the guidance of another person..'Dare to Know'(sapere aude) Have the courage to use your own understanding;this is the motto of the Enlightenment.”

“All our knowledge begins with the senses, proceeds then to the understanding, and ends with reason. There is nothing higher than reason.”

“Enlightenment is man's emergence from his self-imposed nonage. Nonage is the inability to use one's own understanding without another's guidance. This nonage is self-imposed if its cause lies not in lack of understanding but in indecision and lack of courage to use one's own mind without another's guidance. Dare to know! (Sapere aude.) "Have the courage to use your own understanding," is therefore the motto of the enlightenment.”

“For if we regard space and time as properties that must, as regards their possibility, be found in things in themselves, [...] then we really cannot blame the good Bishop Berkeley for degrading bodies to mere illusion. Nay, even our own existence, which would thus be made dependent on the self-subsistent reality of a non-entity such as time, would, along with this time, be changed into mere illusion - an absurdity of which hitherto no one has been guilty.”