Date: Fri, 11 Aug 2006 16:33:43 +0100

From: Steve Hedley

Subject: Law's (Il)logic

So, in summary,

1/ Most references to inductive/deductive reasoning/logic are concerned with factual questions, rather than determining what the law is; though

2/ There are a few references saying that deductive reasoning is one tool for determining common law; however

3/ There are no references ruling out other tools for determining common law (or at least, no-one's produced one yet); and

4/ There are a few (*very* few) attempts to say what those others tools might legitimately be (such as Diplock's "policy").

Steve Hedley
Faculty of Law, University College Cork

-----Original Message-----
From: David Cheifetz
Sent: 11 August 2006 14:29
To: 'Hedley, Steve'
Subject: Law's (Il)logic

A cursory search for usages of any of inductive reasoning, deductive reasoning, inductive logic, deductive logic in Canadian law databases produced a handful of instances (primarily criminal caselaw) in which the judges stated that deciding what conclusions are to be drawn from the facts usually involves inductive reasoning not deductive. I didn't find anything suggesting that, somehow, judicial decision-making may be "alogical" in the sense of being neither inductive or deductive but another mode of mode of moving from evidence or premise to conclusion.

For example, R. v. R.P. (1990), 58 C.C.C. (3d) 334 at 339 (Ont. H.C.J.) [R. v. R.(S.), (1990), 73 O.R. (2d) 355] states "Relevance is a matter of inductive logic requiring that the trial judge examine the proffered evidence in light of his own knowledge and understanding of human conduct: McCormick, ibid., p. 544; Delisle, ibid., p. 10. Relevance is situational and depends not only on the ultimate issue in the case (e.g., identification), but also on the other factual issues which either of the litigants raises as relevant to the ultimate issue."

[McCormick on Evidence, 3rd ed. (1984), p. 544; R. Delisle: "Evidence Principles and Problems", 2nd ed. (1989), p. 10.]

I also found a reference to a mid-30s Australian decision which, I think, asserts that the process of judicial decision-making is scientific and rational because it makes use of inductive reasoning (and implicitly deductive where appropriate). Martin v. Osborne (1936), 55 C.L.R. 367 (High Court of Australia), at p. 385: "The final reason why the question as to the relationship between the fact tendered in evidence and the issue required to be proved is one of 'degree' is that the judgment or inference involved is not one of deductive logic. What is involved is the task of admeasuring the probability or improbability of the fact or event in issue, if we are given the fact or facts sought to be adduced in evidence. A similar scientific and rational inquiry is often required at another stage of the judicial process when the proper inference to be drawn from circumstantial evidence is in dispute."

Finally, I found a mid 1940s Quebec civil case Re Porto Rico Power Co., 26 C.B.R. 170, [1945] 2 D.L.R. 93, [1945] 4 D.L.R. 531 in which a Quebec SC trial judge said about common law as opposed to civil law "in many of them [common law decisions]the decisions are arrived at by a system of inductive reasoning as contrasted with the deductive reasoning of jurists trained under the Civil law system".

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