Page last updated: 2022-05-29 Sun 19:00

Notes on Kant's "Prolegomena to Any Future Metaphysics"

Table of Contents

So, this is basically everything I deemed especially important in Kant's "Prolegomena to Any Future Metaphysics" (this is my first time reading Kant, but, hopefully, not the last; I will update the notes as I read). Some of it is word-by-word citation of the book's contents, some of it is rephrased or commented on. My comments/summaries are marked by this color

1 Introduction (Cambridge edition)

This is a huge infodumping chapter, basically defines the concepts not defined by Kant in the actual text but required for understanding it. Not much to comment on yet, I may only say I'm excited to start reading.

Kant wanted to show that philosophers and natural scientists were not able, and would never be able, to give final answers to questions about the nature of the physical world and of the human mind or soul, and about the existence and attributes of a supreme being.

Hence "Critique of Pure Reason", right?

Sensible and intelligible "worlds":

  • Phenomena - world known via sensory cognition of things as they appear
  • Noumena - world known via intellectual cognition of things as they are is themselves

Space and time - phenomena determined a priori (independently of experience) by the "forms" or laws of human sensibility.

Intellectual cognition of things via the intellect alone proceeds apart from the senses and from the forms of space and time, and grasps the intelligible world of substance through the "form" of its causal relations.

Metaphysics - the science of the first principles in human cognition.

Ontology - science of the "predicates of being", ie of general predicates for describing what does or might have being, or exist (examples: "possible" and "true", "substance" and "accident", "cause" and "effect")

Cosmological topics included the world as a whole, its order and causal structure, the substances composing it, and the relation of natural and supernatural

Psychology considered the existence and properties of the soul or mind, sense, imagination, intellect, freedom of will, immortality of human soul.

Kant considered the impulse toward metaphysics to be as "natural" to human beings as the impulse toward breathing.

Judgments, and propositions expressing those judgments:

Analytic judgment - can be known to be true solely on the basis of the concepts used in the judgment, because the predicate term is already "contained in" the concept of the subject.

(The judgment "ontology is the science of being" could be known to be true solely by reflection on the concept of ontology, for the definiton of the concept includes the meaning "science of being")

Synthetic judgment - the predicate term adds something new to the concept of the subject.

(The judgment "Metaphysics is in trouble" may be true, but "being in trouble" is not part of the very concept of metaphysics)


  • A posteriori - based on sensory experience
  • A priori - known independently of sensory experience

Kant's investigation stands apart from other philosophers because he provided a novel and an especially thorough examination of the powers and capacities, or "faculties", of the human mind, which he explicitly linked to determining the very possibility of metaphysics.

Critique of Pure Reason - attempt to introduce a new question into metaphysics: "Is metaphysics possible?"


  • any systematic body of knowledge
  • usually with the implication that it would be organized around first principles
  • …from which the rest of the body of knowledge might be derived (more or less rigorously)

Mathematics was a model for how scientific expositions of knowledge should be organized. Disciplines like mathematics, metaphysics, theology were all called "sciences".

Intuition - "looking at", "looking upon", a mental representation that is particular (not abstract), and that presents objects concretely (as an image does)Intuitions are contrasted with concepts, which are abstract and general representations, potentially relating to many objects at once.

Manifold of intuition

Manifold - many-fold, indicates a "multiplicity" or something having many parts or elements

Method - method of exposition and method of arguing.

  • Analytic method - starts from a given body of cognition and seeks the principles from which it might be derived (kinda like reverse deduction? have thing1, find rules from which thing1 can be derived)
  • Synthetic method - seeks to establish those principles by direct analysis of the relevant cognitive powers (kinda like induction? have rules1, find the things that adhere to these rules)

"Think an object" - active forming of a mental representation of the chair (object)

  • Subject - thinking subject, the one who is having the thoughts or doing the cognizing
  • Object - either physical object located in space, or the object of thought (the object currently represented in thought, or toward which one's thought is currently directed)

Classical meaning of "skeptic" - someone who sought to suspend judgment on theoretical questions by showing that reason is in conflict with itself

  • Deduction - response to a demand for justification
  • Apperception - awareness of one's own perceptions

Unity of apperception - ability to unify one's perceptions in a single act of consciousness (this is required for the ability of apperception)

Something is "conditioned" by antecedent states of affairs that set the "conditions" for its occurence (heat of the fire is a "condition" that determines the temperature of the soup, the heated soup then being a state of affairs that is "conditioned")

2 Preface

Main question: "Whether such a thing as metaphysics is even possible at all"

If metaphysics is a science, why doesn't it attain lasting acclaim? Why metaphysics perpetually turns round on the same spot? Why are there still no reliable measures with which to distinguish valuable contributions from bullshit?

If not much progress has been made after long cultivation of a science, someone should pose the question whether and how such a science is possible at all.

Hume: how is connection of cause and effect generated by reason? Why if there is one thing, another should always arise? It is wholly impossible for reason to think such a connection a priori and from concepts. Therefore, connection of cause and effect does not come from reason but from imagination and experience. Thus reason has no power to think such connections. Which is so much as to say that there is no metaphysics at all.

Kant: the conclusion is premature, but it is founded on inquiry of sufficient value.

The question: is the connection of cause and effect thought through reason a priori, and in this way has an inner truth independent of all experience (and hence also an extended use not limited to objects of experience)?

Public's reaction to Hume: changing the question from "is the connection of cause and effect independent of all experience" to "whether the concept of cause and effect is right, useful, indispensable"; appeal to common sense (wrong tool for evaluation)

Prolegomena - 'plan' of the Critique of Pure Reason, laid out according to the analytic method (Critique of Pure Reason is composed according to the synthetic method)

So, basically, in Prolegomena we go from concepts to rules (derive rules from concepts). And Critique goes from rules to finding concepts that adhere. And Prolegomena is possible to write exactly because it is written after the Critique, so that Kant has already found the concepts. And evaluating rules from concepts is supposedly easier than finding concepts that adhere to some rules.

3 Preamble

Condition for presenting a body of cognition as science: a distinguishing feature

(otherwise that science is an existing science or intersection of existing sciences)

Distinguishing feature can consist in a difference of the object of cognition, source of cognition, type of cognition.

Sources of metaphysical cognition - cannot be empirical, the principles must be not physical but meta physical, that is, lying beyond experience.

Metaphysical cognition - cognition a priori, or from pure understanding and pure reason.

But since pure understanding and pure reason cannot be differentiated from pure mathematics, metaphysical cognition must be "pure philosophical cognition".

Philosophical cognition - cognition through reason from concepts. Philosophical cognition considers the particular only in the general.

Mathematical cognition - cognition through reason from the construction of concepts. Mathematical cognition considers the general in the particular (particular such as size, angle, etc is kind of 'abstracted away')

Analytic judgment - explicative, adds nothing to the content of the cognition, says nothing except what was actually thought already in the concept of the subject. Common principle - contradiction (predicate of analytic judgment cannot be denied of that subject without contradiction, because the judgment is contained in the definition)

Synthetic judgment - ampliative, augments the given condition, adds something to the concept. Common principle - 'something other than contradiction' (because the judgment is not contained in the definition of concept), although always should be in accordance with the principle of contradiction.

  • Judgments of experience - always synthetic (obvious lol, I wouldn't have to go and experience the judgment if it was analytic and could be derived from principle of contradiction)
  • Mathematical judgments - always synthetic (this one is a bit harder, but basically it is not contained in the concept of 'sum' that 7+5=12, and the concept of sum cannot be analyzed to get a number 12; one must make use of intuition)
  • Properly metaphysical judgments - all synthetic. Judgments belonging to metaphysics (which may be analytic) must be distinguished from properly metaphysical judgments (synthetic, are of substance, are what the science is completely directed)

Metaphysics - directed towards generating cognition a priori in accordance with both intuition and concepts. Metaphysics is directed towards generating philosophical (not mathematical!) synthetic propositions a priori.

4 General question: Is metaphysics possible?

All propositions that are apodictically certain and have never been disputed are analytic. Synthetic propositions are presented, but never proven from bare reason - a priori. One metaphysics always contradicts the other, either in regard to the assertions or their proofs.

Although we can't assume that metaphysics as science is actual, we still have some pure synthetic cognition that is for sure a priori:

  • pure math
  • pure natural science

As both contain propositions fully acknowledged, with some being apodictically certain through bare reason, and others from universal agreement with experience (still independent of experience).

Since we have some (yet?) uncontested synthetic cognition a priori, to derive the possibility of all other synthetic cognition a priori, we don't need to ask whether it (the existing uncontested cognition) is possible, but only: how it is possible.

  • How is pure mathematics possible?
  • How is pure natural science possible?
  • How is metaphysics in general possible?
  • How is metaphysics as science possible? (if it is to be a science, not an art of beneficial persuasions accommodated to general common sense)

5 How is pure mathematics possible?

All mathematical cognition must present its concept beforehand in intuition and indeed a priori; all of mathematical cognition must be grounded in some pure intuition or other, in which it can construct all of its concepts in concreto yet a priori.

Intuition is a representation that depends on the presence of an object.

How is pure intuition possible?

If intuition represented things as they are in themselves, then no intuition a priori would take place, as one can only know what may be contained in the object in itself if the object is present.

The way for (my) intuition to precede the actuality of object and occur as an a priori cognition:

If the intuition contains nothing else except the form of sensibility, which in me as a subject precedes all actual impressions through which I am affected by objects. Then the objects of the senses can be intuited only in accordance with this form of sensibility.

Pure mathematics, as synthetic cognition a priori, is possible only because it refers to no other objects than mere objects of the senses, the empirical intuition of which is based on a pure and indeed a priori intuition (of space and time).

Basically, it is intuition about the objects of senses that is based on a pure a priori intuition of space and time

Space and time - mere forms of our sensory intuition.

6 How is pure natural science possible?

Nature - existence of things (not existence of things in themselves, since then we would not ever understand it a priori or a posteriori).

Experience does not teach the laws of nature: it teaches only what there is and how it is, and not that it necessarily must be so and not otherwise. Therefore it can't teach the nature of things in themselves.

But we still have a pure natural science.

Theory of nature precedes all of physics (which is based on empirical principles), universal natural science is just mathematics applied to appearances, and merely discursive principles (philosophical part).

There are things that are not independependent of sources in experience: motion, impenetrability, inertia, etc. So some of the natural science can't be called completely pure natural science.

But there are also principles that have the universality we require, like "the substance remains and persists", that "everything that happens always previously is determined by a cause" (according to constant laws), and so on. These exist fully a priori.

There is then a pure natural science, so the question is - how is it possible?

Here, the meaning of "nature" is used not in the sense "nature that determines the object" (then things that could never become objects of experience would mess everything up) but in the sense of "nature that signifies conformity to law of existence of things".

Two versions of the question:

How is it possible in general to cognize a priori the necessary conformity to law of things itself as objects of experience?

How is it possible in general to cognize a priori the necessary conformity to law of experience itself with regard to all of its objects?

Solution is the same. Because the subjective laws, under which a cognition of things through experience is possible, also hold for those things as objects of a possible experience.

So it is completely the same, whether you say "a judgment of perception can never be considered valid without a law that if an event is perceived then it is always referred to something preceeding from which it follows according to a universal rule" or "everything of which experience shows that it happens must have a cause".

But it is more appropriate to choose the first formulation, because we can, a priori and previously to any objects being given, have a cognition of conditions under which alone an experience regarding objects is possible, but never of the laws to which objects may be subject in themselves without relation to possible experience. We will therefore be able to study a priori the nature of things in no other way than by investigating the conditions, and the universal laws under which alone such a cognition is possible as experience, and determining the possibility of things as objects of experience accordingly.

Here we seek how the a priori conditions of the possibility of experience are at the same time the sources out of which all universal laws of nature must be derived.

6.1 Notes on video I've watched

Main question: How can metaphysics be possible?

Have to find synthetic, a priori judgments

Transcendental idealism + empirical realism

Rejection of the Noumena: There's clearly a noumena, but that's it

Your mind conforms to the world, the world is how it is out there, and thoughts reflect that <– NOT TRUE!

Objects of experience conform to perception <– TRUE!

There is no "before space and time"


6.2 back to the book, again

Empirical judgments that have objective validity - judgments of experience. Always demand, in addition tothe representations of sensory intuition, special concepts originally generated by understanding: this makes the judgment valid.

Empirical judgments that are only subjectively valid - mere judgments of perception. Do not require a pure concept of the understanding, only the logical connection of perceptions in a thinking subject.

At first, every judgment is a judgment of perception, holding only for us (our subject), and after that we give them a new relation, to an object, and intend that the jubgment should also be valid at all times for us and for everyone else.

Objective validity and necessary universal validity are therefore interchangeable concepts.

Judgments of experience - what experience teaches me under certain circumstances, it must teach me at every time and teach everyone else as well, and its validity is not limited to the subject or its state at that time.

Judgments of perception (subjectively valid) - relation of two sensations to the same subject, and only in the subject's current state of perception, therefore not expected to be valid for the object.

Judgments of experience (objectively valid) - relation of two sensations only to each other.