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to find for metaphysics the grounding that his predecessors had been
unable to find. This refoundation consists, according to Heidegger, in
elucidating the features of human existence in the context of which
human beings™ practical and cognitive access to being is made possible.
What does this have to do with Kant™s enterprise in the metaphysical
deduction of the categories? In the Phenomenological Interpretation of the
Critique of Pure Reason (a lecture course delivered at Marburg in 1927“8,
and first published in 1977) and in Kant and the Problem of Metaphysics
(first edition, 1929), Heidegger develops the following view. Kant™s
groundbreaking insight was to discover that the unity of our intuitions
of space and of time, and the unity of concepts in judgments, have one
and the same ˜˜common root™™: the synthesis of imagination in which
human beings develop a unified view of themselves and of other entities
as essentially temporal entities. Now, categories, according to
Heidegger, are the fundamental structural features of the unifying
synthesis of imagination which results in the unity of time (and space)
in intuition, on the one hand; and in the unity of discursive representa-
tions (concepts) in judgments, on the other hand. This being so, the
fundamental nature of the categories is expounded not in the metaphy-
sical deduction, which relates categories to logical forms of judgments,
but rather in the Transcendental Deduction and even more in
the chapter on the Schematism of the Pure Concepts of the
Understanding. For it is in these two chapters that the role of the
categories as structuring human imagination™s synthesizing (unifying)
of time is expounded and argued for. This does not mean that the
Metaphysical Deduction is a useless or irrelevant chapter of the
Critique. For if it is true that the unity of intuition and the unity of
judgments have one and the same source in the synthesis of imagination
according to the categories, then the logical forms of judgment do give a
clue to a corresponding list of the categories. But this should not lead to
the mistaken conclusion that the categories have their origin in logical
forms of judgment. Rather, logical forms of judgment give us a clue to

those underlying forms or structures of unity because they are the sur-
face effect, as it were, of forms of unity that are also present in sensibility
(where they are manifest as the schemata of the categories) by virtue of
one and the same common root in imagination.44
Note that Heidegger agrees with Cohen at least in maintaining that
logical forms of judgment can provide a leading thread to a table of
categories just because forms of judgment and categories have one and
the same ground, the unity of consciousness. Their difference consists in
the fact that Cohen understands that unity as being the unity of thought
expressed in the principles of natural science. Heidegger understands it
as the unity of human existence projecting the structures of its own
The readings of Kant™s metaphysical deduction we have considered so
far offer challenges only to Kant™s motivation and method in adopting a
table of logical forms of judgment as the leading thread to his table of
categories. What they do not challenge is the relevance of Kant™s
Aristotelian model of logic in developing the argument for his table of
the categories. A more radical challenge comes of course from the idea
that contrary to Kant™s claim, logic did not emerge in its completed and
perfected form from Aristotle™s mind (cf. Bviii). Here we have to make a
quick step back in time. For the initiator of modern logic, Gottlob Frege,
wrote his Begriffsschrift (1879) several decades before Heidegger wrote
Being and Time (1927). Unsurprisingly, by far the more threatening
challenge to Kant™s metaphysical deduction came from Frege™s
Begriffsschrift and its aftermath.
As we saw, Kant takes logic to be a ˜˜science of the rules of the under-
standing.™™ But Frege takes logic to be the science of objective relations of
implication between thoughts or what he calls ˜˜judgeable contents.™™45

See Martin Heidegger, Phanomenologische Interpretation der Kritik der reinen Vernunft, col-
lected edn vol. xxv (Frankfurt-am-Main: Vittorio Klostermann, 1977), pp. 257“303;
Phenomenological Interpretation of the Critique of Pure Reason, trans. Parvis Emad and
Kenneth Maly (Bloomington and Indianapolis: Indiana University Press, 1995),
pp. 175“207. And Kant und das Problem der Metaphysik, collected edn vol. iii (Frankfurt-
am-Main: Vittorio Klostermann, 1991), pp. 51“69; Kant and the Problem of Metaphysics,
trans. Richard Taft (Bloomington: Indiana University Press, 1990), pp. 34“46.
Gottlob Frege, Begriffsschrift. Eine der arithmetischen nachgebildete Formelsprache des reinen
Denkens, in Begriffsschrift und andere Aufsatze (Hildesheim: Olms, 1964). Begriffsschrift, a
formula language for pure thought, modeled upon that of arithmetic, in Frege and Godel: Two
Fundamental Texts in Mathematical Logic, ed. Jean van Heijenhoort (Cambridge, Mass.:
Harvard University Press, 1970). Page references will be to the English edition. On the
distinction between judgment and judgeable content, see ibid., x2, p. 11:

Against the naturalism that tended to become prevalent in nineteenth-
century views of logic, Frege defends a radical distinction between the
subjective conditions of the act of thinking and its objective content.
Logic, according to him, is concerned with the latter, psychology with
the former. In spite of his declared intention not to mix general pure
(¼ formal) logic with psychology, Kant, according to Frege, is confused
in maintaining that logic deals with the rules we (human beings) follow in
thinking, rather than with the laws that connect thoughts independently
of the way any particular thinker or group of thinkers actually think.46
According to Frege, Kant™s subservience to the traditional, Aristotelian
model of subject“predicate logic is grounded on that confusion. For the
subject“predicate model really takes its clue from the grammatical struc-
ture of sentences in ordinary language. And ordinary language is itself
governed by the subjective, psychological intentions and associations of
the speaker addressing a listener. But again, what matters to logic are the
structures of thought that are relevant to valid inference, nothing else.
Those structures, for Frege, include the logical constants of propositional
calculus (negation and the conditional), the analysis of propositions into
function-argument rather than subject“predicate, and quantification.47
In x4 of the Begriffsschrift, Frege examines ˜˜the meaning of distinctions
made with respect to judgments.™™ The distinctions in question are clearly
those of the Kantian table, which in Frege™s time have become classic.
Frege first notes that those distinctions apply to the ˜˜judgeable content™™
rather than to judgment itself.48 This being said, he retains as relevant to
logic the distinction between ˜˜universal™™ and ˜˜particular™™ judgeable

˜˜A judgment will always be expressed by means of the sign , which stands to the left of
the sign, or the combination of signs, indicating the content of the judgment. If we omit the
small vertical stroke at the left end of the horizontal one, the judgment will be transformed
into a mere combination of ideas [Vorstellungsverbindung], of which the writer does not state
whether he acknowledges it to be true or not.™™
Later Frege renounces the expression Vorstellungsverbindung as too psychological, and
talks instead of Gedanke to describe the judgeable content to the right of the judgment
stroke. See the 1910 footnote Frege appended to x2, p. 11, n. 6.
On the rise of nineteenth-century naturalism about logic, and Frege™s conception of logic
as a reaction against naturalism, see Sluga, Frege, especially ch. 1 and 2. In fairness to Kant,
it should be recalled that he does distinguish logic from psychology: he maintains that
contrary to the latter, the former is concerned not with the way we think, but with the way
we ought to think. But this distinction can have little weight for Frege, who wants to free
logic from any mentalistic connotation, whether normative or descriptive.
Strawson™s criticism of the redundancies of Kant™s table is clearly inspired from Frege™s.
See Strawson, Bounds of Sense, pp. 78“82.
It is worth noting that Frege reverses the Kantian terminology and calls ˜˜proposition™™ the
judgeable content and ˜˜judgment™™ the asserted content, whereas Kant reserved the term

contents (Kant™s first two titles of quantity), but leaves out ˜˜singular.™™ He
retains ˜˜negation™™ (Kant™s second title of quality, negative judgment) and
thus the contrasting affirmation (which does not need any specific nota-
tion), but leaves out infinite judgments. He declares that the distinction
between categorical, hypothetical, and disjunctive judgments ˜˜seems to
me to have only grammatical significance.™™ Meanwhile he introduces his
own notation for conditionality in the next section, x5 of the Begriffsschrift
(more on this in a moment). Finally, he urges that the distinction
between assertoric and apodeictic modalities (which alone, he says,
characterize judgment rather than merely the judgeable content)
depends only on whether the judgment can be derived from a universal
judgment taken as a premise (which would make the judgment apodeic-
tic), or not (which would leave it as a mere assertion, or assertoric
judgment), so that this distinction ˜˜does not affect the conceptual
content.™™ Frege presumably means that the distinction between assertoric
and apodeictic judgments does not call for a particular notation in the
Begriffsschrift. As for a proposition ˜˜presented as possible,™™ Frege takes it to
be either a proposition whose negation follows from no known universal
law, or a proposition whose negation asserted universally is false. Although
this last characterization differs from Kant™s characterization of prob-
lematic judgments (as components in hypothetical or disjunctive judg-
ments), it remains that Frege™s view of modality is similar to Kant™s own
view, indeed seems inspired by it. For as we saw Kant thinks that modality
does not concern the content of any individual judgment, but only its
relation to the unity of thought in general. However, Kant does not think
that what we might call this ˜˜holistic™™ view of modality makes it irrelevant to
logic. This point would be worth pursuing, but we cannot do it here.
In short, according to Frege one need retain from the Kantian table
only the first two titles of quantity, the first two titles of quality, and the
second title of modality (assertion expressed by the judgment stroke). To
these he adds his own operator of conditionality, which one might think
has a superficial similarity to Kant™s hypothetical judgment. However,
Frege makes it clear they are actually quite different. He recognizes
explicitly, for instance, that his conditional is not the hypothetical judg-
ment of ordinary language, which he identifies with Kant™s hypothetical
judgment. And he states that the hypothetical judgment of ordinary
language (or Kant™s hypothetical judgment) expresses causality.49
˜˜proposition™™ to assertoric judgment: see above, n. 18; Begriffsschrift, x2, x4. These are
mere terminological differences, but they need to be kept in mind to avoid confusions.
Begriffsschrift, x5, p. 15.

However, his view on this point does not seem to be completely fixed, at
least in the Begriffsschrift, since elsewhere in this text he urges that the
causal connection is expressed by a universally quantified conditional.50
In any event, Kant would not accept any of those statements. For as we
saw, he would say that although the hypothetical judgment does express
a relation of Konsequenz between antecedent and consequent, this rela-
tion is not by itself sufficient to define a causal connection. As for the
universal quantification of a conditional, it would even less be sufficient
to express a causal connection, precisely because the conditional bears
no notion of Konsequenz. So even Frege™s (very brief) discussion of
hypothetical judgment and causality bears very little relation to Kant™s
treatment of the issue.
This might just leave us with Frege™s general complaint against Kant™s
table: the reason this table can have only very little to do with Frege™s
forms of propositions is that it is governed by models of ordinary lan-
guage. Consequently, Frege™s selective approach to Kant™s table does not
merely consist in getting rid of some forms and retaining others. Rather,
it is a drastic redefinition of the forms that are retained (such as the
conditional, generality, assertion as expressed by the judgment stroke).
And this, Frege might urge, is necessary to definitively purify logic of the
psychologistic undertone it still has in Kant. But then one needs to
remember what the purpose of Kant™s table is, as opposed to the purpose
of Frege™s choice of logical constants for his propositional calculus. Frege
sets up his list so that he has the toolbox necessary and sufficient to
expound patterns of logical inference, where the truth-value of conclu-
sions is determined by the truth-value of premises, and the truth-value
of premises is determined by the truth-value of their components (truth-
functionality). Kant™s logic, on the other hand, is a logic of combination
of concepts as ˜˜general and reflected representations.™™ And we might say
that his setting up a table of elementary forms for that logic should help
us understand how the very states of affairs by virtue of which Frege™s
propositions stand for True or False, are perceived and recognized as
such. In fact, I suggest that Frege™s truth-functional propositional logic
captures relations of co-occurrence or non-co-occurrence of states of
affairs that Kant would have no reason to reject, but that for him
would take secondary place with respect to the relations of subordina-
tion of concepts that, when related to synthesized intuitions, allow us to

Ibid., x5, p. 14; x12, p. 27.

become aware of those states of affairs and their co-occurrence in the
first place.
What about Frege™s challenge to the subject“predicate model of judg-
ment and his replacement of it by the function-argument model?51 Here
one might think that the modern logic of relations (n-place functions) is
anticipated by Kant™s transcendental logic, which thus overcomes the
limitations of his ˜˜general pure™™ or ˜˜formal™™ logic. For transcendental
logic is concerned not with mere concept subordinations, but with the
spatiotemporal mathematical and dynamical relations by means of
which objects of knowledge are constituted and individuated. Indeed
the most prolific of Hermann Cohen™s neo-Kantian successors, Ernst
Cassirer, advocated appealing to a logic of relations to capture the
Kantian ˜˜logic of objective knowledge™™ or transcendental logic.52
Examining this suggestion would take us beyond the scope of the pre-
sent chapter. In any event, two points should be kept in mind. The first is
that according to Kant, the relational features of appearances laid out by
transcendental logic are made possible by synthesizing intuitions under
the guidance of logical functions of judgment as he understands them.
In other words, the source of the relations in question is itself
no other than the very elementary discursive functions (functions of
concept-subordination) laid out in his table and guiding syntheses of a
priori spatiotemporal manifolds. The second point to keep in mind
is that however fruitful a formalization of Kant™s principles of transcen-
dental logic in terms of a modern quantificational logic of relations might
be, it does not by itself accomplish the task Kant wants to accomplish with
his transcendental logic and his account of the nature of categories,
which is to explain how our knowledge of objects is possible in general,
and thus explain why any attempt at a priori metaphysics on purely
conceptual grounds is doomed to fail.

Ibid., x9.
See Cassirer, Substanzbegriff und Funktionsbegriff. Peter Schulthess has defended the view
that Cassirer™s emphasis on the relational nature of Kant™s transcendental logic as well as
his emphasis on the ontological primacy of relations, not substances, is in full agreement
with Kant™s own view, including his view of logic. See Schulthess, Relation und Funktion.
Michael Friedman has defended the relevance of Cassirer™s version of neo-Kantianism for
contemporary philosophy of science: see Michael Friedman, A Parting of the Ways: Carnap,
Cassirer and Heidegger (Chicago and La Salle, Ill.: Open Court, 2000), especially ch. 6,
pp. 87“110; and ˜˜Transcendental philosophy and a priori knowledge: a neo-Kantian
perspective,™™ in Paul Boghossian and Christopher Peacocke (eds.), New Essays on the A
Priori (Oxford: Clarendon Press, 2000), pp. 367“84.


On three occasions in the Critique of Pure Reason, Kant takes credit for
having finally provided the proof of the ˜˜principle of sufficient reason™™
that his predecessors in post-Leibnizian German philosophy had sought
in vain. They could not provide such a proof, he says, because they
lacked the transcendental method of the Critique of Pure Reason.
According to this method, one proves the truth of a synthetic a priori
principle (for instance, the causal principle) by proving two things: (1)
that the conditions of possibility of our experience of an object are also
the conditions of possibility of this object itself (this is the argument Kant
makes in the Transcendental Deduction of the Categories); (2) that
presupposing the truth of the synthetic principle under consideration
(for instance, the causal principle, but also all the other ˜˜principles of
pure understanding™™) is a condition of possibility of our experience of
any object, and therefore (by virtue of [1]), of this object itself. What Kant
describes as his ˜˜proof of the principle of sufficient reason™™ is none other
than his proof, according to this method, of the causal principle in the
Second Analogy of Experience, in the Critique of Pure Reason (cf. A200“1/
B246“7, A217/B265, A783/B811).
Now this claim is somewhat surprising. In Leibniz, and in Christian
Wolff “ the main representative of the post-Leibnizian school of German
philosophy discussed by Kant “ the causal principle is only one of the
specifications of the principle of sufficient reason. And Kant himself, in

the pre-critical text that discusses this principle, distinguishes at least
four types of reason, and therefore four specifications of the correspond-
ing principle “ ratio essendi (reason for being, that is, reason for the
essential determinations of a thing), ratio fiendi (reason for the coming
to be of a thing™s determinations), ratio existendi (reason for the existence
of a thing), and ratio cognoscendi (reason for our knowing that a thing is
thus and so).1 Only the second and the third kinds of reasons (reason for
coming to be, reason for existence) are plausible ancestors of the concept
of cause discussed in the Second Analogy of Experience. Why then does
Kant describe as his proof of the principle of sufficient reason a proof
that, strictly speaking, is only a proof of the causal principle, and what
happens to the other aspects of the notion of reason or ground that Kant
discussed in the pre-critical text?
I shall suggest in what follows that in fact Kant™s response to Hume on
the causal principle in the Second Analogy of Experience results in his
redefining all aspects of the notion of reason (and, therefore, of the
principle of sufficient reason): not only the reason for coming to be
and the reason for existing (ratio fiendi and ratio existendi), but also the
reason for the essential determinations of a thing and the reason for our
knowing that a thing is thus and so (ratio essendi and ratio cognoscendi) “ at
least when these notions are applied to the only objects for which one can
affirm the universal validity of some version of the principle of sufficient
reason, the objects of our perceptual experience.
In talking of ˜˜Kant™s deconstruction of the principle of sufficient
reason,™™ what I intend to consider, then, are two things. First, Kant™s
detailed analysis of the notion of ratio (reason, ground) and of the
principle of sufficient reason in his pre-critical text. Second, Kant™s
new definition, in the critical period, of all types of ratio and all aspects
of the principle of sufficient reason.2

These four kinds of reason, ratio, appear in Kant™s Principiorum Primorum Cognitionis
Metaphysicae Nova Dilucidatio, AAi, pp. 391“8; trans. David Walford and Ralf Meerbote, A
New Elucidation of the Principles of Metaphysical Cognition (henceforth New Elucidation), in
Theoretical Philosophy, 1755“1770. Walford and Meerbote translate the Latin ratio by
ground, and thus principium rationis sufficientis by principle of sufficient ground, which
seems odd. I have preferred to keep the term reason, and thus principle of sufficient
reason, despite the more epistemic and less ontological connotation of the term reason.
On this point, see also n. 2.
A point of vocabulary is in order here. The Latin term Kant uses in the 1755 New Elucidation
is ratio. In German, it becomes Grund. ˜˜Principle of sufficient reason™™ is in Latin principium
rationis sufficientis, in German Satz vom zureichenden Grund. Because the word ˜˜reason™™
appears in the ˜˜principle of sufficient reason,™™ I will use the English ˜˜reason™™ for ratio, but

One interesting result of comparing Kant™s pre-critical and critical
views is that a striking reversal in Kant™s method of proof becomes
apparent. In the pre-critical text, Kant starts from a logical/ontological
principle of sufficient reason, moves from there to a principle of suffi-
cient reason of existence (which he equates with the causal principle),
and from there to what he calls a principle of succession (a principle of
sufficient reason for the changes of states in a substance). By contrast, in
the critical text (the Second Analogy of Experience), Kant proves a
principle that looks very much like the principle of succession in the
New Elucidation, which he equates with the causal principle. And in doing
this he declares he is providing ˜˜the only proof™™ of the principle of
sufficient reason of existence and “ I shall argue “ he also redefines the
respective status of the ontological and logical principles themselves. In
short, instead of moving from logic to time-determination, in the critical
period one moves from time-determination to logic. This reversal of
method is related to the discovery of a completely new reason or ground:
the ˜˜transcendental unity of self-consciousness™™ as the reason of reasons,
or the ground for there being any principle of sufficient reason at all.
The discovery of this new ground has striking consequences for Kant™s
critical concept of freedom, which I shall consider at the end of the

The principle of determining reason in Kant™s new explanation
of the first principles of metaphysical knowledge
Kant first defines what he means by ˜˜reason™™ or ˜˜ground™™ (ratio). His
definition places this notion in the context of an analysis of propositions,
or rather, of what makes propositions true.3 It is in this context that he

sometimes add ˜˜ground™™ in parenthesis, to avoid any confusion with the faculty of reason (in
German, Vernunft). In the texts from the early 1760s, logischer Grund and Realgrund are
usually translated ˜˜logical ground™™ and ˜˜real ground,™™ so in discussing these texts I shall
often switch to ˜˜ground.™™
By ˜˜proposition,™™ Kant means what he calls in the critical period ˜˜assertoric judgment,™™
namely a judgment asserted as true. A judgment for Kant is the content or the intentional
correlate of an act of judging. If I judge that the world contains many evils, ˜˜the world
contains many evils™™ is the content of my act of judging. It is also a proposition, a judgment
asserted as true. If I merely entertain the thought that the world may contain many evils,
without taking the statement ˜˜the world contains many evils™™ to be true, then the content of
my thought is a mere judgment, not a proposition, in Kant™s vocabulary. To move from a
mere judgment to a proposition (a judgment held to be true), one needs a reason. This,
then, is the context in which Kant defines his notion of ˜˜reason™™ or ˜˜ground.™™

explains why he prefers to speak of ˜˜determining™™ rather than ˜˜suffi-
cient™™ reason:
To determine is to posit a predicate while excluding its opposite. What
determines a subject with respect to a predicate is called the reason. One
distinguishes an antecedently and a consequently determining reason. The
antecedently determining reason is that whose notion precedes what is
determined, i.e. that without which what is determined is not intelligi-
ble.* The consequently determining reason is that which would not be
posited unless the notion of what is determined were already posited
from elsewhere. The former can also be called reason why or reason for
the being or becoming (rationem cur scilicet essendi vel fiendi); the latter can
be called reason that or reason of knowing (rationem quod scilicet
* To this one may add the identical reason where the notion of the
subject determines the predicate through its perfect identity with it, for
instance a triangle has three sides; where the notion of the determined

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