Famous Immanuel Kant Quotes Explained
Immanuel Kant was a German philosopher of the Enlightenment born in Konigsberg, Prussia. Kant's most-quoted lines are mostly stripped from longer arguments in the three Critiques and the Groundwork. Below are eight, with notes on what they actually claim.
“Two things fill the mind with ever new and increasing admiration and awe, the more often and steadily we reflect upon them: the starry heavens above me and the moral law within me.”
Two things fill the mind with ever-increasing wonder and awe, the more often and the more intensely the mind of thought is drawn to them: the starry heavens above me and the moral law within me.
What it means
The closing remark of the Critique of Practical Reason (1788), and inscribed on Kant's tombstone. The "starry heavens above" represents the order of nature investigated by science; the "moral law within" represents the order of freedom investigated by ethics. Kant's claim is that both point to dimensions of reason's reach beyond mere sensory experience.
“Act only according to that maxim whereby you can, at the same time, will that it should become a universal law.”
Der kategorische Imperativ, der überhaupt nur aussagt, was Verbindlichkeit sei, ist: handle nach einer Maxime, welche zugleich als ein allgemeines Gesetz gelten kann.
What it means
The first formulation of the Categorical Imperative, from the Groundwork of the Metaphysics of Morals (1785). Kant's test asks whether the principle behind one's action could be coherently adopted by everyone: if universalising the maxim destroys it — as universal lying destroys promising — the action is morally impermissible.
Attributed to Immanuel Kant:
“Enlightenment is man's emergence from his self-imposed immaturity.”
What it means
The opening sentence of Kant's essay "What is Enlightenment?" (1784). "Immaturity" (Unmündigkeit) is the inability to use one's understanding without another's guidance; it is "self-imposed" because the cause is cowardice and laziness, not lack of intellectual capacity. The motto of Enlightenment, Kant adds, is Sapere aude! — "dare to know."
“Out of the crooked timber of humanity, no straight thing was ever made.”
Idea for a General History with a Cosmopolitan Purpose (1784), Proposition 6. | Variant translations: Out of timber so crooked as that from which man is made nothing entirely straight can be built. | From such crooked wood as that which man is made of, nothing straight can be fashioned. | Never a straight thing was made from the crooked timber of man.
What it means
From "Idea for a Universal History with a Cosmopolitan Purpose" (1784). Kant's image is that human nature contains an unsociable element that cannot be eliminated, so political institutions must be designed for beings with this permanent twist rather than for the perfectly rational beings of moral theory. Isaiah Berlin later revived the phrase as a moral-political theme.
“All our knowledge begins with the senses, proceeds then to the understanding, and ends with reason.”
All human knowledge begins with intuitions, proceeds from thence to concepts, and ends with ideas.
What it means
From the introduction to the Critique of Pure Reason (1781/1787). Kant's sequence is deliberate: sensation provides the raw material, the understanding organises it into concepts, and reason draws inferences. He is rejecting both pure empiricism, which stops at sensation, and pure rationalism, which proceeds without it.
Attributed to Immanuel Kant:
“Act in such a way that you treat humanity, whether in your own person or in the person of any other, always at the same time as an end and never merely as a means.”
What it means
The "humanity formulation" of the Categorical Imperative, from the Groundwork (1785). Persons, having the capacity for rational self-determination, possess what Kant calls "dignity" rather than "price," and may never be used merely as instruments for someone else's purposes. The formulation is the philosophical root of much modern human-rights discourse.
“Thoughts without content are empty, intuitions without concepts are blind.”
A 51, B 75
What it means
From the Critique of Pure Reason. Kant is stating the central thesis that knowledge requires the cooperation of two faculties: sensible intuition (which supplies particular content) and the understanding (which supplies general concepts). Either one without the other produces no cognition.
Attributed to Immanuel Kant:
“He who is cruel to animals becomes hard also in his dealings with men.”
What it means
From Kant's Lectures on Ethics, compiled by students in the 1770s and 1780s. Kant did not extend full moral status to animals, but argued that cruel treatment of them damages the moral sensibility of the person who is cruel. The position is sometimes called the "indirect duty" view.