A Closer Look at Rationalism


Rationalism is the contradictory of empiricism in so far as it denies the importance of experience in science.


By Fr. Raymond Taouk,



I.  the schools


1) the greeks


1.    The Eleates (Parmenides) refuse experience since it leads to error whereas reason leads to truth.  The first of all truths is the principle of identity ‘being is, non-being is not’ from which he builds the monist philosophy of a being unique and immobile.

2.    The Stoic morality is a morality of indifference and insensibility to pleasure, suffering and passions.  Such ethics is based on the same principles as Parmenides.  It states that happiness is found in virtue, virtue is to live according to right reason, and to live reasonably is to be God.



2) the moderns


1.    Descartes is rationalist by the theories of :


·      universalised mathematics which must apply its a priori method (rigorous and scientific) to physics and metaphysics. 

·      the clear ideas : Maths is the type of all sciences since it progresses a priori through ideas clear and distinct obtained by intuition, from which all else is deduced a priori.  Experience does not furnish its objects to science but serves only to corroborate the scientific conclusions.

·      the origin of ideas : clear ideas are innate in us but potential.[1]


2.    Spinoza, Leibniz, Wolf :

·      All follow Descartes in extending  to all sciences the method of  mathematics.

·      Leibniz admits also the virtual innate ideas, including the sensible representations.


3.    Kant, leaving aside his idealism, professes a phenomenalist (inherited from Hume) rationalism. All knowledge needs two necessary elements :

·      the form, which is the sum total of laws inscribed inside the subjects.  It is given a priori.

·      the matter, which is the content of knowledge.  It is given a posteriori, by experience.

·      in the end, rationalism is the winner since the mind, with its impressions received, the raw data,  constructs definite objects which are both real and intelligible.  Sense data give only disordered and subjective impressions; the form gives reality and intelligibility.


4.    Kant’s successors absorb the matter of knowledge into the form : only reason gives the knowledge of truth:

·      Hegel, by the dialectic method, explains the entire world, ‘Panlogism’,

·      Fichte, by the activity of an impersonal reason, explains the scientific knowledge.



ii.  general diagram of knowledge









innate ideas

experience alone





senses dirctly, int. by abstraction.



inductive empiric.

deductive mathem

1º induction; 2º deduction


object in se

sensible only

essences indpdt fr. sensible

sensible and mat. essces


last object

subjective phenom.

innate forms (idealism)



iii.  Arguments and refutation


1)     arguments of innatism


1.    Descartes:

·      in Metaphysics, denies that the body could act upon the spirit, because non est actio distans.

·      in Psychology, denies that any real triangle can ever correspond to a mental triangle.


2.    Leibniz :

·      refuses experience : man is a substance, and therefore a monad w/o door or windows, i.e. he knows only by what is already within himself : nisi ipse intellectus.

·      experience has no necessity : it presents only facts, but not the property of necessity, condition of science.  Thus, this necessity, which does not come from experience, must be drawn out of one’s intellect.


3.    Kant :

·      a universal and necessary judgement cannot be founded on experience or knowledge a posteriori.

·      a useful judgement cannot be analytical (i.e. jdgt in which the Predicate is included in the Subject).

·      Thus, the only judgement which is both necessary and useful is the synthetic a priori judgement, based on reason and not on experience (since they are a priori) nor on the principle of contradiction (since they are synthetic judgements).[2]


2)     critique of the rationalistic arguments.


1.    Leibniz :


·      bases his innatism on his Metaphysics which accepts no transitive actions, which is sufficient proof of the uselessness of his Mphs. The denial of transitive actions can only lead to innate idealism.

·      Brunschvicg says that relation exists, yet it does not come from experience but from the mind.  We answer that, although the essence ‘relation’ is a mental abstraction, the concrete relations are objects of experience, e.g. a harmony, a contrast of colours.

·      Is the intellect an innate faculty? the intellective faculty is innate, yes, but as such, it cannot be known since it is known only when it is actuated by the apprehension of an object : w/o exper., no ideas.


2.    Kant :

·      in general : There is something a priori which is a given for any faculty, and that is the formal object, ie. some aspect of all things knowable by that particular faculty (colours for sight, material essences for the int.). Yet all that is known is obtained by experience.  However, when Kant says that the formal element is given a priori, he means that the faculty gives a form which sensible data do not have.

·      in particular :

·      Can we say that the intellect brings to our experience a form which it didn’t have?  No!  the intellect does not purely and simply ‘make the universality’ bec. if the int. gives universality, it gives it to a pre-existing concrete essence/form, and simply abstracts an essence which exists concretely in reality and abstractly in the mind : this is the old ‘problem of the universals’.

·      the analytical judgements are a priori true, i.e. the truth of the judgement can be affirmed with no recourse to experience.  However, the separate concepts of the analytical judgement (whole-greater-part) have been abstracted from experience.

·      the synthetic a priori judgements of Kant are wrong since :

·      in fact, every judgement is both analytical if it is to be true (P=S), and synthetic since even in tautology where the mind distinguishes the predicate from the subject (P=/=S) : the 2 terms are logically or verbally distinct and really identical.[3]

·      to define the analytical and synthetic judgt according as ‘the concept-predicate is or is not included in the concept-subject’ is an idealist presupposit : it pretends that the idea is object of knowledge ‘id quod cognoscitur’, and not the means of knowledge ‘id quo res cognoscitur’.[4] The real and true judgement must go beyond the mental concept and reach reality since it consists in uniting two aspects of the same thing.

·      Kant simplifies the complexity of thought : there are 5 predicamental relations, not 2.

·      ‘a priori’ is said properly of a demonstration from the cause to the effect ‘a priori ad posteriorem’, and inversely for the ‘a posteriori’ demonstration ‘a posteriori ad priorem’.  Abusively applied to jdgt, we speak of a priori to designate the judgement in necessary matter (4 predicables), and a posteriori for a contingent judgement (predicb.5).

·      the synthetic a priori judgements are not judgements, they are exactly what we call prejudices.  They judge something without having examined the thing to be judged, wo the only foundation of a valid judgment and truth : the intuition of the thing (direct for the judgements per se nota, indirect or demonstrative for the demonstrated judgements).  A judgement is not scientific, ie. universal and necessary, by a subjective a priori form but by the intellectual intuition of the essences abstracted from experience.


iv. discussion of rationalism


1.    Pro: it shows

·      the innatism of the intellect and its natural spontaneity.

·      the a priori of the truth of the first principles.

·      the transcendence of the intellectual knowledge over sensible knowledge (principles & concepts exist).


2.    Contra : it denies one of two :

·      the passivity of the human spirit which can think only after it has received an object from the senses.

·      either partially or totally the role of experience  (Spinoza, Hegel) :

·      partially, and it justifies its position by saying that experience provides him only with particular facts.  But the rationalist can make such a statement only from experience!

·      totally, and it affirms that experience provides the mind with no object, and knowledge can only be given a priori.  But such an a priori knowledge is the denial of an evident experience and is founded on an a priori, i.e. on nothing!


3.    Refutation :

·      Descartes :

·      his universal mathematics is rationalist because it defines the method of knowledge wo relation to its object. 

·      Arbitrarily, he wants to extend to all sciences a method valid for mathematics: but what is used to solve the problems of the abstract quantity may not square with other objects.

·      The unique mathematical a priori method leads[5]either to deny the existence of any object which doesn’t fit the method, or to declare it unknowable, absurd or irrational.

·      Hegel dogmatises that knowledge must be systematic, and this one essentially dialectic, but :

·      nothing obliges us to enter such a system, repugnant to reason since the dialectic method is a torture, and certainly not the only method of knowledge,

·      nothing guarantees that the system is true and exhaustive.  A system which is both idealist (every being is not if it is not thought) and pantheistic (human reason = divine reason = omniscient) may be a coherent system, but it is certainly not true.


4.    Conclusion : Because it did not accept empiricism, rationalism refused at the same time the Aristotelian theory of abstraction, and was led to draw its concepts and ideas from the intellect itself.  Only abstraction is able to escape the dilemma and conflict between the two opposite schools of thought.





[1] “Je les tire en quelque sorte du trésor de mon esprit”.  For Desc., only these innate ideas are clear.

[2]On what are these judgements grounded? on reason broadly said, i.e. the form of knowl, forms of sensibility,  and the categories of understanding (vs. reasoning, object of Mph.).  The first found the mathematical jdgts, the 2d the jdgts of physics.

[3]e.g. ‘this bottle is Whisky’ is a judgt of  distinct terms each of which designates the same thing.

[4]cf. I 85,2.

[5] Cf. Positivism, Scientism, Phenomenology, Hegel & Marx follow the a priori rationalistic method of knowledge.