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Part of the book series: Studies in the History of Philosophy of Mind ((SHPM,volume 16))

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Leibniz repeatedly states that there is a very close connection between reflection and rationality. On his view, reflective acts somehow lead to self-consciousness, reason, the knowledge of necessary truths, and even to the moral liability of the respective substances. Whereas it might be relatively easy to see how reflective acts lead to self-consciousness, it is much harder to understand how they are connected to rationality. Why should a substance which is able to produce reflective acts therefore be rational? How can having reflective acts be responsible for the substance’s ability to reason correctly and to acquire knowledge of necessary and eternal truths? My aim in this paper is to understand better the required mechanisms and to thus make conceivable Leibniz’s bold claim that reflective acts lead to rationality. In order to accomplish this, I will proceed in three steps. First, I will specify what kind of self-consciousness, according to Leibniz, is produced by reflective acts. A substance must recognize itself as a unitary substance bearing perceptions. Second, I will argue that this type of self-consciousness can be seen as the basis for the ability to form judgments. This is possible because the subject-predicate structure of judgments is mirrored by the ontology of substances and their modifications. Third, I will point out that, together with the idea of identity (which we also acquire by reflection), the combination of judgments allows us to make inferences. This ability, in turn, is sufficient for rationality. Thus, I can explain how reflective acts and rationality are connected with each other.

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  1. 1.

    For example, a dog that sees a stick immediately thinks of the pain it felt when it saw the stick the last time. See for this Principles of Nature and Grace Based on Reason (henceforth PNG) §5/AG 208: “There is interconnection among the perceptions of animals which bears some resemblance to reason, but this interconnection is only founded in the memory of facts or effects, and not at all in the knowledge of causes. That is why a dog runs away from the stick with which he was beaten, because his memory represents to him the pain which the stick caused him.” Similarly, in New Essays on Human Understanding (henceforth NE) 2, 11, 11/RB 143, Leibniz writes: “Beasts pass from one imagining to another by means of a link between them which they have previously experienced. For instance, when his master picks up a stick the dog anticipates being beaten. […] This could be called ‘inference’ or ‘reasoning’ in a very broad sense. But I prefer to keep to accepted usage, reserving these words for men and restricting them to the knowledge of some reason for perceptions’ being linked together. Mere sensations cannot provide this: all they do is to cause one naturally to expect once more that same linking which has been observed previously, even though the reasons may no longer be the same. Hence those who are guided only by their senses are frequently disappointed.”

  2. 2.

    For Leibniz it cannot just be a brute fact that some creatures are rational while others are not. Because of his commitment to the Principle of Sufficient Reason, there must be some explanation for this fact. For more on rationalism and the Principle of Sufficient Reason see Della Rocca (2003).

  3. 3.

    We will see later whether or not Leibniz is justified in putting forward such a thesis.

  4. 4.

    As we have seen Leibniz speaks of self-awareness, reasoning, and the knowledge of necessary truths for example in PNG §5. In NE 2, 21, 5/RB 173 he restricts the faculty of understanding (entendement) and the ability to have thoughts (pensées) to minds. The term ‘thought’, however, is ambiguous in Leibniz. Aside from this narrow use that is restricted to rational beings, there is also a broader use of the term, where ‘thought’ just designates any perception whatsoever. See for this NE 2, 1, 10/RB 111: “[A]ction is no more inseparable from the soul than from the body. For it appears to me that a thoughtless state (un estat sans pensée) of the soul and absolute rest in a body are equally contrary to nature, and never occur in the world.” Thus, in the broader sense, even completely confused perceptions count as thoughts.

  5. 5.

    That rational substances enter into a society with God, Leibniz says in Monadology §84/AG 223–224 and in PNG §§14–15/AG 211–212. For personhood and moral liability, see DM §34/AG 65–66.

  6. 6.

    This is clear from the part of DM §34/AG 65–66 that is quoted above.

  7. 7.

    The knowledge of necessary truths of course presupposes the ability to form propositions as well.

  8. 8.

    For more on this topic, see McRae (1976), Kulstad (1991), Simmons (2001), Jorgensen (2009), and Jorgensen (2011).

  9. 9.

    For more on Descartes on modes see Hattab (2009). For the medieval understanding of accidents, see Normore (2009).

  10. 10.

    Cf. PNG §1/AG 207.

  11. 11.

    Cf. Monadology §14/AG 214.

  12. 12.

    Cf. NE 2, 21, 4/A VI, vi, 172.

  13. 13.

    It is fairly common to read the Aristotelian categories as having both a semantic and an ontological dimension. See for example Oehler (2006), 102.

  14. 14.

    Ockham, for example, strictly distinguishes between the (ontological) inherence relation on the one hand and predication on the other hand. Cf. Summa Logicae I, 32/OP I, 94. For this, see also Perler (1994).

  15. 15.

    Di Bella (2005), 255 speaks of Leibniz’s “logico-ontological inesse relation.”

  16. 16.

    For a brief discussion of this passage, see Di Bella (2005), 255.

  17. 17.

    For more on the inesse relation in Leibniz see Di Bella (2005), 253–255 and Schneider (1989). Schneider emphasizes the double role the inesse relation plays in Leibniz’s philosophy, both as a logical and a metaphysical relation: “Damit wird die ganze Spannbreite des Leibnizschen Ansatzes deutlich: Inesse soll so allgemein angesetzt werden, daß es seine wichtige Funktion als eine der wesentlichen Relationen innerhalb von Logik und Metaphysik erfüllen kann (indem der hier wichtige Begriff des Requisits herangezogen wird), andererseits aber seine Bindung an die ursprüngliche anschauliche Vorstellungen des räumlichen Enthaltenseins nicht verlieren” (Schneider [1989], 364).

  18. 18.

    This is clear from Monadology §35/AG 217: “And there are, finally, simple ideas, whose definition cannot be given. There are also axioms and postulates, in brief, primitive principles, which cannot be proved and which need no proof. And these are identical propositions, whose opposite contains an explicit contradiction.”

  19. 19.

    Similarly, in NE Preface/RB 51 Leibniz writes: “Perhaps our gifted author [i.e., Locke] will not entirely disagree with my view. For after devoting the whole of his first book to rejecting innate illumination, understood in a certain sense, he nevertheless admits at the start of his second book, and from there on, that ideas which do not originate in sensation come from reflection. But reflection is nothing but attention to what is within us, and the senses do not give us what we carry with us already. In view of this, can it be denied that there is a great deal that is innate in our minds, since we are innate to ourselves, so to speak, and since we include Being, Unity, Substance, Duration, Change, Action, Perception, Pleasure, and hosts of other objects of our intellectual ideas?”

  20. 20.

    Does it make sense to say that an idea that is innate is discovered by us? For Leibniz it does. With respect to very general metaphysical innate ideas such as being and identity, he points out that “we do not always pay particular attention to them, and that it takes time to sort them out” (NE 1, 3, 3/RB 102). Thus, we do not actually acquire the idea of identity by reflection when we reflect – we rather discover it. See for this point, Jolley (2005), 109: “It is plausible to suppose that, for Leibniz, reflection on the mind’s properties, such as unity or identity, is not strictly the means by which an idea is acquired; it serves rather as the stimulus which activates the dispositional property of the mind in which the relevant idea consists. Thus what happens in post-natal acts of reflection is that the mind first comes to conscious awareness of an idea which it has always possessed.”

  21. 21.

    One might worry at this point that reflection only gives us the idea of identity over time but not the idea of identity which is required for the laws of logic (thanks to Jari Kaukua for pointing this out to me). One way to respond to this worry is to say that, if the identity that is needed in order to conceive of the logical laws is synchronic identity, then we get it for free as soon as we have diachronic identity since synchronic identity can be considered a limiting case of diachronic identity. Another strategy would be to argue that there is no equivocation between different senses of identity at all but only different applications of the same concept of identity. The fact that we have the idea of identity in virtue of reflecting on our substantial selves does not imply that we are only equipped with one special notion of identity (namely identity over time). Rather, reflection is just the way our (dispositional) innate idea of identity simpliciter is actualized.

  22. 22.

    See for this Jolley (2005), 109 again. See also note 20.


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Bender, S. (2016). Reflection and Rationality in Leibniz. In: Kaukua, J., Ekenberg, T. (eds) Subjectivity and Selfhood in Medieval and Early Modern Philosophy. Studies in the History of Philosophy of Mind, vol 16. Springer, Cham.

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