Critique of Pure Reason

I had to deny knowledge in order to make room for faith.

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

Whereas the beautiful is limited, the sublime is limitless, so that the mind in the presence of the sublime, attempting to imagine what it cannot, has pain in the failure but pleasure in contemplating the immensity of the attempt.

Thoughts without content are empty, intuitions without concepts are blind.

Man must be disciplined, for he is by nature raw and wild...

Skepticism is thus a resting-place for human reason, where it can reflect upon its dogmatic wanderings and make survey of the region in which it finds itself, so that for the future it may be able to choose its path with more certainty. But it is no dwelling-place for permanent settlement. Such can be obtained only through perfect certainty in our knowledge, alike of the objects themselves and of the limits within which all our knowledge of objects is enclosed.

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.

it was the duty of philosophy to destroy the illusions which had their origin in misconceptions, whatever darling hopes and valued expectations may be ruined by its explanations.

Two things fill the mind with renewed and increasing awe and reverence the more often and the more steadily that they are meditated on: the starry skies above me and the moral law inside me. I have not to search for them and conjecture them as though they were veiled in darkness or were in the transcendent region beyond my horizon; I see them before me and connect them directly with the consciousness of my existence.

All human cognition begins with intuitions, proceeds from thence to conceptions, and ends with ideas.

It is the Land of Truth (enchanted name!), surrounded by a wide and stormy ocean, the true home of illusion, where many a fog bank and ice, that soon melts away, tempt us to believe in new lands, while constantly deceiving the adventurous mariner with vain hopes, and involving him in adventures which he can never leave, yet never bring to an end.

Human reason, in one sphere of its cognition, is called upon to consider questions, which it cannot decline, as they are presented by its own nature, but which it cannot answer, as they transcend every faculty of the mind.

Our age is the age of criticism, to which everything must be subjected. The sacredness of religion, and the authority of legislation, are by many regarded as grounds of exemption from the examination of this tribunal. But, if they on they are exempted, they become the subjects of just suspicion, and cannot lay claim to sincere respect, which reason accords only to that which has stood the test of a free and public examination.]

But, above all, it will confer an inestimable benefit on morality and religion, by showing that all the objections urged against them may be silenced for ever by the Socratic method, that is to say, by proving the ignorance of the objector.

Metaphysics... is nothing but the inventory of all we possess through pure reason, ordered systematically. Nothing here can escape us, because what reason brings forth entirely out of itself cannot be hidden, but is brought to light by reason itself as soon as reason's common principle has been discovered. The perfect unity of this kind of cognition, and the fact that it arises solely out of pure concepts without any influence that would extend or increase it from experience or even particular intuition, which would lead to a determinate experience, make this unconditioned completeness not only feasible but also necessary. Tecum habita, et noris quam sit tibi curta supellex. Dwell in your own house, and you will know how simple your possessions are.

Every beginning is in time, and every limit of extension in space. Space and time, however, exist in the world of sense only. Hence phenomena are only limited in the world conditionally, the world itself, however, is limited neither conditionally nor unconditionally.

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?

Deficiency in judgement is properly that which is called stupidity; and for such a failing we know no remedy. A dull or narrow-minded person, to whom nothing is wanting but a proper degree of understanding, may be improved by tuition, even so far as to deserve the epithet of learned. But as such persons frequently labour under a deficiency in the faculty of judgement, it is not uncommon to find men extremely learned who in the application of their science betray a lamentable degree this irremediable want.

Never wish to see a just cause defended with unjust means.

That all our knowledge begins with experience there can be no doubt. For how should the faculty of knowledge be called into activity, if not by objects which affect our senses and which, on the one hand, produce representations by themselves or on the other, rouse the activity of our understanding to compare, connect, or separate them and thus to convert the raw material of our sensible impressions into knowledge of objects, which we call experience? With respect to time, therefore, no knowledge within us is antecedent to experience, but all knowledge begins with it. But though all our knowledge begins with experience, is does not follow that it all arises from experience. For it is quite possible that even our empirical knowledge is a compound of that which we perceive through impressions, and of that which our own faculty of knowledge (incited by sense impressions) supplies from itself, a supplement which we do not distinguish from that raw material until long practice and rendered us capable of separating one from the other. It is therefore a question which deserves at least closer investigation and cannot be disposed of at first sight: Whether there is any knowledge independent of all experience and even of all impressions of the senses? Such knowledge is called 'a priori' and is distinguished from empirical knowledge, which has its source 'a posteriori', that is, in experience...

For if the question is absurd in itself and demands unnecessary answers, then, besides the embarrassment of the one who proposes it, it also has the disadvantage of misleading the incautious listener into absurd answers, and presenting the ridiculous sight (as the ancients said) of one person milking a billy-goat while the other holds a sieve underneath.

Experience may teach us what is, but never that it cannot be otherwise.

Philosophical knowledge is knowledge which reason gains from concepts; mathematical knowledge is knowledge which reason gains from the construction of concepts.

On the seeming futility of metaphysics. Why then has nature afflicted our reason with the restless striving for such a path, as if it were one of reason's most important occupations? Still more, how little cause have we to place trust in our reason if in one of the most important parts of our desire for knowledge it does not merely forsake us but even entices us with delusions and in the end betrays us! Or if the path has merely eluded us so far, what indications may we use that might lead us to hope that in renewed attempts we will be luckier than those who have gone before us?

To know what questions may reasonably be asked is already a great and necessary proof of sagacity and insight. For if a question is absurd in itself and calls for unnecessary answers, it not only brings disgrace to the person raising it, but may prompt an incautious listener to give absurd answers, thus presenting, as the ancients said, the laughable spectacle of one person milking a he-goat, and another holding the sieve underneath.

There is no freedom, but everything in the world takes place entirely according to nature....Transcendental freedom is therefore opposed to the law of causality, and represents such a connection of successive states of effective causes, that no unity of experience is possible with it. It is therefore an empty fiction of the mind, and not to be met with in any experience. We have, therefore, nothing but nature, in which we must try to find the connection and order of cosmical events. Freedom (independence) from the laws of nature is no doubt a deliverance from restraint, but also from the guidance of all rules. For we cannot say that, instead of the laws of nature, laws of freedom may enter into the causality of the course of the world, because, if determined by laws, it would not be freedom, but nothing else but nature. Nature, therefore, and transcendental freedom differ from each other like legality and lawlessness. The former, no doubt, imposes upon the understanding the difficult task of looking higher and higher for the origin of events in the series of causes, because their causality is always conditioned. In return for this, however, it promises a complete and well-ordered unity of experience; while, on the other side, the fiction of freedom promises, no doubt, to the enquiring mind, rest in the chain of causes, leading him up to an unconditioned causality, which begins to act by itself, but which, as it is blind itself, tears the thread of rules by which alone a complete and coherent experience is possible.

...by saying that the former was only concerned with quality, the latter only with quantity, mistook cause for effect.

Two things fill the mind with every new and increasing wonder and awe, the oftener and the more steadily I reflect upon them: the starry heavens above me and the moral law within me. I do not merely conjecture them and seek them as if they were obscured in darkness or in the transcendent region beyond my horizon: I see them before me, and I connect them directly with the consciousness of my own existence. The starry heavens begin at the place I occupy in the external world of sense, and they broaden the connection in which I stand into an unbounded magnitude of worlds beyond worlds and systems of systems and into the limitless times of their periodic motion, their beginning and duration. The latter begins at my invisible self, my personality, and exhibits me in a world which has true infinity but which only the understanding can trace - a world in which I recognise myself as existing in a universal and necessary ( and not, as in the first case, only contingent) connection, and thereby also in connection with all those visible worlds. The former view of a countless multitude of worlds annihilates, as it were, my importance as an 'animal creature' which must give back to the planet (a mere speck in the universe) the matter fro which it came, matter which is for a little time endowed with vital force, we know not how. The latter, on the contrary, infinitely raises my worth as that of an 'intelligence' by my being a person in whom the moral law reveals to me a life independent of all animality and even of the whole world of sense, at least so far as it may be inferred from the final destination assigned to my existence by this law, a destination which is not restricted to the conditions and boundaries of this life but reaches into the infinite.

If the intuition must conform to the nature of the objects, I do not see how we can know anything of them a priori. If, on the other hand, the object conforms to the nature of our faculty of intuition, I can then easily conceive the possibility of such an a priori knowledge.

We have seen, therefore, that I am not allowed even to *assume*, for the sake of the necessary practical use of my reason *God, freedom, immortality*, unless at the same time *I deprive* speculative reason of its pretensions to transcendent insights. Reason, namely, in order to arrive at these, must employ principles which extend only to objects of possible experience, and which, if in spite of this they are applied also to what cannot be an object of experience, actually always change this into an appearance, thus rendering all practical *expansion* of pure reason impossible. Hence I had to suspend *knowledge* in order to make room for *belief*. For the dogmatism of metaphysics without a preceding critique of pure reason, is the source of all that disbelief which opposes morality and which is always very dogmatic.