Abstract
In his book ‘Natural Law and Natural Rights’ John Finnis states that there are seven basic values -i.e. life, knowledge, play, aesthetic experience, sociability (friendship), practical reasonableness and ‘religion’ (the quotation marks are Finnis’ own) which are universal and valid in se. Of course different people may think differently about these basic values, but they are not really open to discussion: “Here each one of us, however extensive his knowledge of the interests of other people and other cultures, is alone with his own intelligent grasp of the indemonstrable (because self-evident) first principles of his own practical reasoning”1.
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Notes
J. Finnis, 1980, p.85. For the mentioned basic values, see p.86 ff.
The predicate logic’ is constantly regarded by me as ‘formal logic’, unless distinguishing epitheta indicate otherwise.
This is connected with the ’universalizability of normative judgements (cf R.M. Hare, 1967–1, p.7 ff.), at least insofar as these judgements are not random imperatives, but have a reason. Insofar as it is not important for the pretension of correctness by whom this correctness is pretended, the reason which I put forward as justification is necessarily intersubjective.
The Dutch author J.B.M. Vranken (1978, p.310) puts forward as an objection to formal logic, that it does not reach the main question as to in what way the contents of the primary statements, resp. premisses, is established, and which guarantees can be given for the correctness of these.
For ‘true’ can be read ‘normative valid’ insofar as the premisses express judgements which give norms. There is to be distinguished between the ‘being valid’ of e.g. a legal norm and the logically ‘being valid’ of a rule of inference, a scheme for inferring based on the latter or an argument produced by interpretation of the variables in such a scheme.
This completeness has been proven by Gödel, 1930. The statement of completeness is not to be confounded with the statement of in completeness, which was also proven by Gödel, one year later: this concerns the impossibility to completely formalise a particular theory (arithmetic) within the elementary predicate calculus. See Gödel, 1931.
The standard formalization which is often found is: if and only if p ⊃ ((-pvq)⊃q) is a logical tautology; this formula is, however, equivalent to the formula which is given in the text.
In modal and deontic logic, however, this is dependant on the question, which has been left aside here, as to what extent these systems are complete and reliable: insofar as this is less the case silent semantic presuppositions play a bigger part, which is detrimental to the logical character of the constants concerned.
Beth, 1948, p.7
Perelman, 1961, in Perelman 1963, p.219.
Horovitz, 1972, p.105. My agreement with this quotation is an agreement with the point of view that the formal character of logic is a sequel of the definition; a different question is whether the definition is correct. I believe that it is very questionable to define logic’ as an investigation for the conditions of the rational force of arguments and then to infer from this that logic must therefore be formal: it is at the least defensible that ‘rationality’ has substantial (non-formal) aspects as well. I therefore prefer a definition of ‘logic’ according to which logic deals with the conditions for validity of arguments, a definition which, if ‘validity is regarded in the way it continuously has been in the text, necessarily leads to a formal logic, but which, on the other hand leaves the range of ‘rational’ completely open. This range will be discussed in the last chapter.
Cf. Kahane, 1973, p.9.
P.W. Brouwer, R.M. Themis 1982, p.33. has pointed at an error in the original Dutch edition of this book, an error which has been corrected in this text.
I have the strong impression that this meaning of ‘non-formal’ and ‘material’ logic lies at least enclosed in what adherents to such a logic give to it as a task. Perelman e.g. notes that ‘the specific problems of legal logic (and legal logic is a non-formal logic with him,S) do not occur when we deal with the deduction of conclusions which logically follow from a set of premisses, but when we deal with the establishment of these premisses themselves, thereby giving an exact import to the legal norms’ (Perelman, 1966, in Perelman, 1970, p.128).
This point of view is most clear in e.g. Perelman, 1961, in Perelman, 1963, p. 218 ff. See particularly p.221 ff., in which Perelman defends the non-formal character of the ‘legal logic’ with the argument that legal reasoning is not either compulsory or not, but relevant or not relevant, strong or weak, while he, reversily, connects formal logic to the ’mathematical proof or to the ‘demonstrative arguments of the mathematicians’.
This impression is at least often made on me. E.g. in Perelman, 1971, p.6 and 7 where he states that since Descartes only ‘the mathematical demonstration, the conclusive proof, which by its evidence imposes itself upon every reasonable being’ has been considered worth to pay attention to. Just as when faced with evidence the difference of opinion disappears, he continues, does this Cartesian way of regarding a reasoning make the idea of a reasonable choice itself contradictory. ‘For the arguments which justify our wishes, our choices and our decisions are never as compulsory as the demonstrative proofs are: they are more or less strong, pertinent, convincing. While a demonstration is either valid or invalid, imposes itself absolutely or is deprived of any value at all, it is always possible with argumentation to argue for and against...’. I cannot interpret this otherwise than that here Perelman wishes to leave out the deductive ways of reasonings when choices etc. are at issue, with the argument that a choice can never be compulsory, and that he, in doing so, forgets that a deductive inference cannot ever be compulsory (in the sense of: no longer open to reasonable challenge) either, unless -as never or the same sense.
As Perelman does e.g. in the quotation in the foregoing note and in several other places.
See Perelman, 1961, in Perelman, 1963, p.222.
In my text I have continuously used ‘compulsory1 in the sense of ‘deductive-logically valid’, not in the other sense of ’the conclusion is no longer open to challenge’. In other words: I was aiming at a compulsory reasoning, not at a compulsory conclusion.
Insofar as formal logic is concerned, only its meaning for reasonings were at issue in this and the foregoing sections.
The meaning of formal logic is, however, not exhausted by this. Formal systems may also be regarded as theories concerning particular concepts, which are included in the formal systems as constants and of which the meaning is syntactically reconstructed within these systems. In this way e.g. a modal logic may be considered as a theory on ‘necessary’, ‘possible’ and ‘impossible’, and a deontic logic as a theory on ’obligator/, ‘permitted’ and ‘prohibited’. Theories such as these are in that case naturally of eminent importance to reasoning in which such concepts are used.
Perelman therefore rightly wonders what specifically legal aspect of ‘legal logic’ remains if ‘logic’ is interpreted formally. See e.g. Perelman, 1968, in Perelman, 1970, p.133.
It is possible to think of the system which was developed in Hohfeld, 1923. In sectors of the law specific systems, which are built around a number of concepts which are cardinal to this sector, may possibly be very meaningful. Cf. also Lindahl, 1977.
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Soeteman, A. (1989). Logic. In: Logic in Law. Law and Philosophy Library, vol 6. Springer, Dordrecht. https://doi.org/10.1007/978-94-015-7821-9_1
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