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  • Foto del escritorÁlvaro R. G. Barredo

Communicability and the Common Grounds of Reason: Revisiting the Kantian concept of Belief

Actualizado: 19 jul 2021

“Wenn jemand nicht beweisen kann, daß ein Ding ist, so mag er versuchen zu beweisen, daß es nicht ist. Will es ihm mit keinem von beiden gelingen (ein Fall, der oft eintritt), so kann er noch fragen: ob es ihn interessire, das Eine oder das Andere (durch eine Hypothese) anzunehmen, und dies zwar entweder in theoretischer, oder in praktischer Rücksicht”. [1] - Immanuel Kant, The Metaphysics of Morals. (AkVI, 354)

1. Introduction

This opening quote points straight into the crux of what can be, at times, perplexing about the work of Immanuel Kant. The rigour with which he tries to draw the limits of human reason in the First Critique seems to show a sharp contrast with his approval of rational faith in God in the Second and Third Critiques, so far so that some have doubted of the honesty of his postulates of practical reason, with Heinrich Heine famously calling Kant’s practical reason a “magic wand” (Palmquist, 1992).

Given these oddities, the question whose answer will be sought in this essay is: can we find a common ground for knowledge and faith in Kant’s epistemology? We will see that Kant finds this linking bridge, not in shared factual merits, since faith has no place in expanding theoretical reason (AkV, 134), but in our ability to communicate both knowledge and faith to rational beings in general, given a series of provisos that can qualify both as justified beliefs. To reach this conclusion, we will analyse what the distinctive features of Kant’s faith are, whether the different categories of faith he presents can be subsumed under a single set of conditions, and, finally, how the merits required from faith can be linked to those of knowledge.

2. Faith and self-awareness

One may ask whether it is even relevant to talk about the epistemic status of faith (Glaube) in Kant’s work, to which the answer yielded by the author seems to be, unambiguously, affirmative. Not only does he chide superstition for being uncalled for in a rational religion (AkVI, 167-168) but, more importantly to us, in the First Critique he makes a distinction between persuasion, which he rejects as mere self-defection (AkIII, 531), and faith, towards which he is far less aggressive.

Persuasion and faith, prima facie, seem to be practically alike. Both are characterised as objectively insufficient and subjectively sufficient (ibid.). Objective insufficiency, as Chignell exposes, means that they both are beliefs that “[do] not render the relevant proposition objectively probable enough to be held with a moderate-to-high degree of confidence by a rational subject” (Chignell, 2007). How are these two categories of belief, then, different? Precisely, as mentioned before, Kant holds persuasion as defection. That is, adapting Chignell’s scheme for analysis:

(P) Subject S1 is persuaded by p if and only if:

  1. S1 believes that p, and

  2. S1 has certain grounds g1 on which he bases p, and

  3. g1 is objectively insufficient for asserting p, and

  4. if asked, on reflection, S1 would cite g1 as objective grounds for p.

The sense in which S1 is self-defected is that, despite p being objectively insufficient, S is (perhaps willingly) unaware of that fact. By contrast:

(F) S2 has faith in q if and only if:

  1. S2 believes that q, and

  2. S2 has certain grounds g2 on which she bases q, and

  3. g2 is objectively insufficient for asserting q, and

  4. if asked, on reflection, S2 would acknowledge that g2 is objectively insufficient for asserting q.

In other words, the distinctive feature of faith in Kant’s view is an awareness of the epistemic status that the proposition q has, while, still, believing in it (Odero, 1992: pp. 166, 176). This, however, can seem weird. Why would someone believe something while, at the same time, acknowledging its insufficiency?

3. Goal-oriented beliefs and blame

Kant exposes the possibility of such a mental state with an example. Imagine a doctor that is fairly sure that his patient will die if left untreated, but who knows that the gravity of the patient’s state will not allow him to conduct a proper diagnosis. He has to act quickly, so he gives his patient a treatment for tuberculosis, even though the only evidence for that malady that the doctor has is lack of evidence against it (AkIII: 534).

The doctor’s belief in the patient having tuberculosis falls under the category of faith rather than persuasion because he is fully aware that, had the case been less dramatic, he would have paid more attention to giving an objectively grounded diagnosis and that, on retrospect, he may very well retract, based on better evidence, this belief.

Furthermore, since it is reasonable to think of epistemic justification in terms of blame, in the sense of, on the one hand, being responsible for holding unjustified beliefs (Clifford, 1876); and, on the other, of being absolved for the consequences of a justified belief being false; in the case of the doctor, despite Kant not saying it explicitly, if there were no possible way for him to diagnose the patient properly, we can be pretty certain that Kant’s intention-driven ethics would not condemn him. Therefore, given the circumstances, the doctor was justified in adhering to that faith, insofar he is aware of its insufficiency.

This justification stems from the fact that one could not possibly blame the doctor for acting in the best way that the environment he was working under allowed him to, and for adhering to a pragmatic faith (AkIII, 534), the first category of faith considered by Kant, without which the patient would not have had any chance at surviving. Remember, however, that this implies that the doctor does not have compelling reasons to believe that the patient, in actuality, does not have tuberculosis (ibid.). If that were the case, then the doctor would be saying that the only way to save the patient is to assume that he has an illness which the doctor is pretty sure he does not have! If we are to allow this, then he could as well give him an aspirin saying that the patient only has a headache.

Thus, it is best to say that the belief in the patient having tuberculosis is justified granted that we seek the patient’s survival. Indeed, if, rather than a doctor trying to save the patient, the relevant subject were an unempathetic alien studying the prevalence of certain causes of death in human beings, the alien would not be justified at all in believing that it is tuberculosis – he would take his time to carefully study the disease that affects this person, indifferent to whether the person lives or dies.

That possible abuse of faith is denounced by Kant as a principle of “lazy reason” (AkIII, 453-454) and it, in short, entails that one cannot properly have faith in a result that a given investigation or action is supposed to yield. In other words, the doctor is justified in believing that the patient has tuberculosis, because, without that belief, there is no chance that the patient will live; but he is not justified in believing that the treatment will have the same success likelihood as if he were sure of the diagnosis – that belief is not necessary for the goal and, therefore, is unjustified. This point about the necessity of a belief, deemed by Kant “hypothetically necessary” (AkIII, 533) by virtue of the goal, gives us the tools we need in order to analyse the conditions of the justification of faith.

(FJ) S2 is justified in having faith in q when pursuing a goal G if and only if:

  1. S2 has no compelling reasons to think that q is not true, and

  2. if asked, on reflection, S2 would acknowledge the objective insufficiency of q, and

  3. q is, as far as S2 can be reasonably expected to know, necessary in order to achieve G.

Notice that this significantly restricts the possible scope of justified faith: only hypothetically necessary propositions constitute justified objects of faith. With this, we can rephrase our definition of faith like so:

(F’) S2 has faith in q if and only if:

  1. S2 believes q, and

  2. S2 is pursuing a goal G, and

  3. S2 is justified in having faith in q when pursuing a goal G.

Indeed, as far as Kant is concerned, faith has to be justified; otherwise, it assumes some deception, which turns it into persuasion. This deception needs not be direct: one could be persuaded about p being necessary for achieving G, which would violate condition (iii) of (FJ) – S is, reasonably, expected to be able to know better, yet he persuades himself into not doing it. Faith, and this will be important later, does not depend on particular conditions of the believer (AkIII: 531).

It is worth reiterating the connection of this view of faith and blame. If, granted a given goal, we accept that the person in question had no way to proceed than by giving her assent to a given proposition, and we know she acknowledges the purely instrumental status of the belief instead of being deluded by it, then she cannot be blamed at all by the belief, since (a) she is not hypostasising this pragmatic assent by claiming any objective reality to it, and (b) she is forced by the circumstances to accept it.

Note that merely wanting something to be true is outright unacceptable for Kant as grounds for faith; he puts the example of an idealistic lover who wants his perfect loved one to exist, which Kant disregards as being a delusion that comes from mere inclination (AkV, 143), it does not logically follow from a goal he committed to. This does not necessarily mean that all pragmatic faith must be a tool for the theoretical. Chignell points out a plausible example of having faith in one’s son not being "a hardcore drug user" granted that one’s goal is to have a good relationship with the son (Chignell, 2007).

From this general framework, the true nuance of Kant’s conception of faith starts to be seen. A second category of faith, deemed “doctrinal” by Kant (AkIII, 534) is characterised by its goal being, specifically, the completion of a given scientific endeavour (AkIII, 535). Thus, the general scheme we presented earlier for the conditions of faith needs not be changed to accommodate for doctrinal faith, since its only difference is that it refers to a particular genre of goals.

However, this kind of faith does entail a peculiarity. Earlier, it was contingent circumstances that did not allow us to achieve objective sufficiency to our beliefs; now, it is the limits of human reason. This – and the problems thereby entailed – is best exemplified by Kant’s infamous quote from the Third Critique: “it results absurd for man to even conceive [...] or hope that, eventually, a Newton capable of making even the production of a weed comprehensible with regard to ordered laws may appear” (AkV, 400). From this impossibility, Kant argues, the belief in a teleologically ordered natural world becomes necessary in order to proceed with natural sciences (AkV, 418). This example is particularly relevant because it has become duly dated. Nevertheless, Chignell argues (op. cit.), this stems out of Kant’s historical context; indeed, it would have been unreasonable to expect, at the time when Kant wrote, a biologist to know about the theory of evolution by natural selection; this makes faith in a teleologically ordered world justified for 18th century natural scientists, fulfilling condition (3.) of (FJ).

With this, we reach the most illustrious category of Kantian faith, moral faith. This features, most prominently, faith in God, the afterlife and freedom (vid. Book II of the Second Critique), but, also, the continuous progress of humankind towards a moral civilisation (AkVIII, 309). All of these, according to Kant, follow as necessary beliefs if one is to pursue the moral law.

Moral faith is very similar to doctrinal faith, save for one aspect: the goal on which these beliefs lie is a duty. Once again, the difference between moral faith and the formerly analysed types of belief is simply the kind of goal that they imply. The acknowledgment of objective insufficiency is still a must.

We have now seen that the three categories of Kantian faith fall under the same justifying conditions (FJ) and, thus, we have drawn a full picture of the epistemological exigences Kant imposes onto faith for it to constitute a valid object of our reason. We can finally answer the question this essay aims to assess.

4. Justification as communicability

Is there a way to incorporate both knowledge and faith under the same conditions for justification? The key for answering this lies in the assessment Kant makes of knowledge as a distinct kind of belief. The distinctive feature of knowledge is its objective sufficiency, and this is characterised by “the possibility of communicating (emphasis added) it and checking its validity for all human reason” (AkIII, 532).

If you have a true belief but you are incapable of communicating it, as far as Kant is concerned, it is not knowledge; in other words, justification for knowledge implies communicability. This seems intuitive; if a belief is justified, it means that it not merely “based on the subjective nature of the individual” (AkIII, 531). On the other hand, mere persuasion – Kant explicitly states – cannot be communicated (ibid.).

Now, faith is not communicable in the same way as knowledge (Odero, 1995: p. 182), since you cannot make somebody have faith (ibid.: p. 188); faith is always characterised as an endeavour pertaining to the subject, since only he can set his goals (AkVI, 305). Nonetheless, we have already seen that the merits Kant requires of faith are such that the specific characteristics of the individual play no role in it; faith follows logically from the goal one is committed to (FJ), and the justifiedness of faith is, therefore, communicable to all rational beings. We can imagine the distinct statuses of persuasion and faith by imagining a conversation between people who hold those beliefs. P being a persuaded person; F, someone that holds faith in something; and A, an “agnostic” to that object of faith:

  • P: “The natural world shows immense beauty and order, therefore, God has to exist!”

  • A: “I am not convinced by that; we cannot explain why the world is how it is, but there may be reasons outside our comprehension that would clarify it”. (AkVI, 400).

P’s persuasion is not universally communicable, because he claims that his assertion is objectively sufficient when, in reality, it is not, which leads to flawed arguments, unacceptable to rational observers. Compare it to the following exchange:

  • F: “I do not know whether God actually exists or not, but I am a taxonomist and I am striving to chart the different structures of the natural world; so far, every living being I have found has shown order, and, since I cannot possibly imagine any other way in which this can be the case [2], I have faith in an intelligent creator that ensures I will always find order in nature.”

  • A: “Since I am not a taxonomist, I do not adhere to that faith, but I can see how I would probably do it if I were one.”

Faith has its particular way of communication (Odero, 1995: p.196), inasmuch as it is made clear that, were the interlocutor to commit to the same goals, she would also have such faith, so:

(C) S’s belief in b is communicable if and only if any rational person.

  1. committed to the goals relevant to b, and

  2. with the same access to relevant information as S would adhere to it (ibid.).

Persuasions are not communicable because they come, not from the goals to which S is committed or the information available to her, but from her subjective inclinations and nature. Faith, on the other hand, as derived from (FJ), is limited to the logical (necessary) consequences of the relevant goal.

This concept of justification as communicability forms the bridge between knowledge and faith. Knowledge is categorically, not hypothetically sufficient (AkIII: 88-89), which means that it does not have relevant goals attached to it; that is, it is always communicable if information is available. Faith, on the other hand, is communicable insofar any rational person can agree that the belief would logically follow if (1.) and (2.) of (C) were true in her or his particular case (for instance, if we (1.) sought to classify animals in a taxonomy and (2.) lived before Darwinian evolution was posited). In that way, justification as communicability can be seen as the common ground of the epistemic claims deemed acceptable by Kantian philosophy.

5. Conclusion

Behind the seeming oddities of Kant’s “extended” concept of justification, systematicity and unity lie, showing a nuanced conception of how we understand the merits of beliefs. Kant’s notions are, after all, very intuitive: a belief is justified if you do not believe it just because of your personal preferences, but because of objective circumstances that beset you, which are not limited to questions of fact, but also include necessary implications of the goals one is committed to – for instance, moral law.

If this is the case, it follows that you could make any other rational being accept, if not adhere by it, the conditional validity of your belief. By analysing Kant’s system from this approach, we can be more sympathetic towards certain claims of his philosophy that, otherwise, would perhaps shock us as dated or plainly wrong. Knowledge and faith both need to be justifiable to rational beings in general, that is, under Kant’s view, they need to be communicable.

The “magic wand” of practical reason has turned out to be, after all, rather disenchanted.


[1] “If one cannot prove that something is the case, he can try to prove otherwise. If he achieves neither (which often happens), one can still ask if it is in his interest to accept [...] one thing or the other, with a theoretical or practical purpose”.

[2] This exchange would have occurred, hypothetically, in Kant’s time, so, without the possibility of knowing about Darwinian evolution.


  • CHIGNELL, Andrew (2007): “Belief in Kant”, in The Philosophical Review, 116(3), pp. 323-360.

  • CLIFFORD, W. K. (1876): “The Ethics of Belief”, in Contemporary Review, 29, pp. 289-309.

  • KANT, Immanuel (1787): Crítica de la Razón Pura. Transl. Pedro Ribas, Barcelona: Penguin Random House Grupo Editorial, S.A.U., 2015.

  • -----------, (1788): Crítica de la Razón Práctica. Transl. Roberto R. Aramayo, Madrid: Alianza Editorial, S.A., 2013.

  • -----------, (1790): Crítica del Discernimiento. Transl. Roberto R. Aramayo and Salvador Mas, Madrid: Machado Grupo de Distribución, S.L., 2016.

  • -----------, (1793): “En torno al tópico: «tal vez eso sea correcto en teoría, pero no sirve para la práctica»”, in Teoría y Práctica, Transl. M. Francisco Pérez López and Roberto R. Aramayo, Madrid: Editorial Tecnos (Grupo Anaya S.A.), 2011.

  • -----------, (1793): La Religión dentro de los límites de la mera Razón, Transl. Felipe Martínez Marzoa, Madrid: Alianza Editorial, S.A., 2016.

  • -----------, (1797): La Metafísica de las Costumbres, Transl. Adela Cortina Orts and Jesús Conill Sancho, Madrid: Editorial Tecnos (Grupo Anaya S.A.), 2016.

  • ODERO, José Miguel (1992): La fe en Kant. Barañáin-Pamplona: Ediciones Universidad de Navarra.

  • PALMQUIST, Stephen (1992): “Kant’s “appropriation” of Lampe’s God”, in The Harvard Theological Review, 85(1), pp. 85-108.

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