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Limits of human knowledge

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Often appears with: reason and the intellect · doubt, skepticism, and certainty · logic, method, and demonstration · the problem of evil and theodicy · perception and the senses · simple ideas · providence and divine governance · whole vs part · transcendental inquiry · transcendent ideas (god, freedom, immortality) · the passions and the emotions · the nature and attributes of God

Usually: argument (9) · crisis of belief (7) · skepticism (7) · detachment (4) · exhortation (4) · reflection (2) · dialogue (1) · injustice endured (1) · curiosity (1) · reverence (1)

Quotable
“But this land is an island, and enclosed by nature herself within unchangeable limits.” Immanuel Kant, The Critique of Pure Reason · vivid
“But in whatever direction we pursue our researches, whether in time or space, we discover everywhere the clear proofs of a Creative Intelligence, and of His foresight, wisdom, and power.” Charles Lyell, Principles of Geology · insight
“Persons almost entirely unacquainted with the powers of a machine cannot be expected to guess at its effects.” Thomas Robert Malthus, An Essay on the Principle of Population · observation
“Which we are not at all to wonder at, since we having but some few superficial ideas of things, discovered to us only by the senses from without, or by the mind, reflecting on what it experiments in itself within, have no knowledge beyond that, much less of the internal constitution, and true nature of things, being destitute of faculties to attain it.” John Locke, An Essay Concerning Humane Understanding, Volume 1 · insight
“I have been able to measure some of your globes, know their paths, assign the laws of motion; but I have not been able to learn who you are.” Voltaire, Voltaire's Philosophical Dictionary · insight
“I have been able to measure some of your globes, know their paths, assign the laws of motion; but I have not been able to learn who you are.” Voltaire, Voltaire's Philosophical Dictionary · observation

The Critique of Pure Reason primary

Immanuel Kant · 1781–1787
SECTION I. OF SPACE > part, external. To the question *How?* we are no more able to reply, (4/15)

Kant argues that reason investigates God, freedom, and immortality because these transcend experience, yet metaphysics initially proceeds dogmatically, so philosophy must ask how a priori cognition is possible and what its limits and value are.

III. Philosophy stands in need of a Science which shall Determine the Possibility, Principles, and Extent of Human Knowledge “à priori” Of far more importance than all that has been above said, is the consideration that certain of our cognitions rise completely above the sphere of all possible experience, and by means of conceptions, to which there exists in the whole extent of experience no corresponding object, se…

The Critique of Pure Reason primary

Immanuel Kant · 1781–1787
SECTION I. OF SPACE > Chapter III Of the Ground of the Division of all Objects into Phenomena and Noumena (1/31)

Kant frames human knowledge as an “island” of truth within fixed limits, surrounded by an “ocean” of illusion, and argues that before sailing further we must justify our claims and the bounds of cognition.

We have now not only traversed the region of the pure understanding and carefully surveyed every part of it, but we have also measured it, and assigned to everything therein its proper place. But this land is an island, and enclosed by nature herself within unchangeable limits. It is the land of truth (an attractive word), surrounded by a wide and stormy ocean, the region of illusion, where many a fog-bank, many an i…

The Critique of Pure Reason primary

Immanuel Kant · 1781–1787
SECTION I. OF SPACE > Chapter III Of the Ground of the Division of all Objects into Phenomena and Noumena (23/31)

Kant says understanding limits sensibility without expanding it: it can think an object-in-itself only as a transcendental object, a cause of phenomena, but without categories it yields empty, limit-marking representation and no knowledge.

denied, in the absence of a determinate conception of them, but, as no category is valid in respect of them, neither must they be admitted as objects for our understanding. Understanding accordingly limits sensibility, without at the same time enlarging its own field. While, moreover, it forbids sensibility to apply its forms and modes to things in themselves and restricts it to the sphere of phenomena, it cogitates…

The Critique of Pure Reason primary

Immanuel Kant · 1781–1787
SECTION I. OF SPACE > Section II. The Discipline of Pure Reason in Polemics (10/14)

Kant argues that recognizing ignorance can motivate inquiry: some ignorance concerns things, some concerns limits of knowledge, and only critical (a priori) grounds can show ignorance is necessary.

*Scepticism not a Permanent State for Human Reason.* The consciousness of ignorance—unless this ignorance is recognized to be absolutely necessary ought, instead of forming the conclusion of my inquiries, to be the strongest motive to the pursuit of them. All ignorance is either ignorance of things or of the limits of knowledge. If my ignorance is accidental and not necessary, it must incite me, in the first case, t…

An Essay Concerning Humane Understanding, Volume 1 secondary

John Locke · 1689
BOOK I NEITHER PRINCIPLES NOR IDEAS ARE INNATE > CHAPTER XXIII. (16/18)

Locke argues that we can know nothing beyond simple ideas gained from sensation and reflection, so even body, immaterial spirits, and God are known only through those limited ideas.

32. We know nothing of things beyond our simple Ideas of them. Which we are not at all to wonder at, since we having but some few superficial ideas of things, discovered to us only by the senses from without, or by the mind, reflecting on what it experiments in itself within, have no knowledge beyond that, much less of the internal constitution, and true nature of things, being destitute of faculties to attain it. A…

An Essay Concerning Humane Understanding, Volume 2 primary

John Locke · 1690 (2nd volume in Essay Concerning Human Understanding)
BOOK III. OF WORDS. > CHAPTER III. (11/17)

Locke says people are ignorant because they lack the simple ideas they need; humans only receive ideas from sensation and reflection, which may be far less than other beings could have.

FIRST, There are some things, and those not a few, that we are ignorant of, for want of ideas. First, all the simple ideas we have are confined (as I have shown) to those we receive from corporeal objects by sensation, and from the operations of our own minds as the objects of reflection. But how much these few and narrow inlets are disproportionate to the vast whole extent of all beings, will not be hard to persuad…

Thoughts of Marcus Aurelius Antoninus primary

Marcus Aurelius Antoninus · c. 167–180 CE
letter which is now extant may be one of those which Tertullian (28/43)

The passage claims that the universe is administered by God’s providence, then addresses the problem of evil by arguing that apparent disorders cannot disprove an intelligent, wise order governing all things.

that we can discern the providence which rules the world, if we possess two things,--the power of seeing all that happens with respect to each thing, and a grateful disposition. But if all things are wisely ordered, how is the world so full of what we call evil, physical and moral? If instead of saying that there is evil in the world, we use the expression which I have used, "what we call evil," we have partly antic…

Principles of Geology secondary

Charles Lyell · Composed as a long-running edition/author’s revision culminating in the 9th edition; prefaced May 24, 1853.
BOOK I. (CHAPTERS I. TO XIII.) > CHAPTER L. (21/22)

In concluding remarks, Lyell reflects on geology’s inability to find a beginning of earth history, argues by analogy that creation may have finite limits, and asserts evidence of a Creative Intelligence.

beings may already have peopled the land and water, has been declared to be equivalent to the assumption that there never was a beginning to the present order of things. With equal justice might an astronomer be accused of asserting that the works of creation extended throughout *infinite* space, because he refuses to take for granted that the remotest stars now seen in the heavens are on the utmost verge of the mat…

An Essay on the Principle of Population primary

Thomas Robert Malthus · 1798 (composed in 1798; dated 7 June 1798 within the text)
CHAPTER 1 > CHAPTER 12 (5/9)

Malthus argues that more unlikely claims about immortality are no more plausible than four eyes and hands, and says unexpected discoveries require analogies from prior facts to be philosophically grounded.

no more genuine indications that man will become immortal upon earth than that he will have four eyes and four hands, or that trees will grow horizontally instead of perpendicularly. It will be said, perhaps, that many discoveries have already taken place in the world that were totally unforeseen and unexpected. This I grant to be true; but if a person had predicted these discoveries without being guided by any anal…

The Confessions of St. Augustine primary

Augustine, of Hippo, Saint · Composed during Augustine’s episcopate at Hippo, largely 397–400 (Book I opens with prayer typical of the initial composition).
BOOK I > BOOK XI (3/18)

Augustine considers how Moses’ testimony about creation can be trusted, arguing that inward Truth recognizes what is true beyond languages, and he contrasts the mutability of heaven and earth with God’s uncreated goodness and knowledge.

in Whom are hidden all the treasures of wisdom and knowledge. These do I seek in Thy books. Of Him did Moses write; this saith Himself; this saith the Truth. I would hear and understand, how "In the Beginning Thou madest the heaven and earth." Moses wrote this, wrote and departed, passed hence from Thee to Thee; nor is he now before me. For if he were, I would hold him and ask him, and beseech him by Thee to open th…

Theodicy primary

Gottfried Wilhelm Leibniz, Freiherr von · 1710-1711
book with much acrimony. But the accused won his case in a Synod. > PART TWO (24/80)

Leibniz continues by praising divine bestness and the limits of human knowledge, then urges faith in God’s order by comparing coherent wholes (organisms) with partial observations (broken parts).

were too fortunate; and Herodotus in some passages hints at his belief that all Divinity is envious; which, however, is not in harmony with the doctrine of the two principles. 137. Plutarch, in his treatise *On Isis and Osiris*, knows of no writer more ancient than Zoroaster the magician, as he calls him, that is likely to have taught the two principles. Trogus or Justin makes him a King of the Bactrians, who was co…

Voltaire's Philosophical Dictionary secondary

Voltaire · 1734-08-01/1764-12-31
SECTION I > SECTION II (7/24)

Voltaire criticizes encyclopedic systems of physics and theology by staging a dialogue where Nature confesses she is “all art,” and the Philosopher concludes that human reason cannot reach first principles.

of France the heirs of Charles I., Louis XIV.'s first cousins, etc., etc.; a hundred like examples set my ideas in disorder, and I know no longer where I am. A: Well, do storms stop our enjoyment of to-day's beautiful sun? Did the earthquake which destroyed half the city of Lisbon stop your making the voyage to Madrid very comfortably? If Attila was a brigand and Cardinal Mazarin a rogue, are there not princes and m…