Q. What are the Comment on the role of formal logic in English law.
It is important to differentiate ‘formal logic’ and ‘legal reasoning’. The former involves a scientific approach to problems of induction and deduction; the latter is an imprecise description of a common attitude to the determination of a legal dispute. The answer ought to show how far formal logic is used in a judgment, and attention should be directed to some of the problems involved in attempts to apply a rigid system of rules to legal procedure. The following skeleton plan is used as a framework for the answer:
Introduction – definition of logic – its restricted use in law –
the Aristotelian syllogism – inflexibility of formal logic –
reasoning in adjudication – references in judgments to logic – argument by analogy – logic and prevention of
inconsistency – arguments concerning logic and control –
Dewey’s warning on logic and law – the danger of
abandoning logic in the law – conclusion referring to the
‘Hand formula’ and jurimetrics.
We define logic, for the purposes of this answer, as a science that is concerned with the canons and criteria of validity in thought and demonstration. It is a methodology, a technique, enabling conclusions to be drawn from information presented in a specific, prescribed manner. In English law, it plays a restricted role and is never used as the sole rationale of a legal decision, so that it is unlikely for a judgment to rest on the belief that the ‘plaintiff has demonstrated the logical superiority of his case’. Almost invariably, its use is qualified, as will be illustrated below. Reference will be made to those who believe that an extended use of logic, as the basis of a scientific approach to the law, is desirable.
There are several different types of logic; in Europe, Aristotelian logic is dominant. Aristotle taught that logic was ‘the science of sciences’, that is, a methodological introduction to the other sciences. It necessitated ‘thinking about thinking’ and involved a system of rules by which deductive thought might be represented and analysed. The essence of deduction involves the derivation of a conclusion from a set of statements (‘premises’). Aristotle advocated the use of the syllogism – a formal scheme of demonstration. A simple example is as follows: (1) All A is B; (2) Some C is A; (3) Therefore, some C is B. There are here three ‘categorical propositions’, containing only three terms (A, B and C), with each of the terms appearing in two statements. (By comparison, ‘inductive logic’ involves reasoning from particular statements to a general truth.)
The rules of logic are precise, inflexible and systematic. They are, therefore, incapable of modification to suit particular circumstances. ‘Logic with a changing content’ is a contradiction in terms. To seek to modify the rigid rules of logic is as unproductive as an attempt to solve a problem in terms of Euclidean geometry by ‘changing’ Euclid’s fundamental propositions. Hence, syllogistic reasoning is not always adequate for the representation or solution of a problem in English law, and, save for some trivial matters, it is rarely possible to compress the essence of a complex legal problem within the unyielding framework of a formal syllogism. Indeed, if the schemes of formal logic were applicable to the analysis and resolution of disputes, then settlement would be possible in a mechanical way without the intervention of legal procedures. X’s dispute with Y arising from Y’s alleged invasion of X’s property rights might be resolved swiftly and correctly by reference to an exact, immutable system of logical propositions. It is precisely because this cannot be done that the process of adjudication becomes necessary. This is not to say that the use of ‘reasoning’ has merely a minor role in the legal process. But ‘reasoning’ and the application of formal logic must be differentiated. Thus, a judicial decision which is clearly ‘unreasonable’, that is, irrational, will not stand – a principle enunciated in Associated Provincial Picture Houses Ltd v Wednesbury Corp (1948); a finding which ‘flies in the face of the facts’ would be difficult to sustain. This is far removed, however, from situations in which purely formal logic is used in the solution of a problem. Strict logical rules cannot be utilized to ‘make’ decisions in English law, if only because the disputed facts are often imprecise and ‘untidy’ and cannot be presented in the exact form required for the exercise of those rules. Thus, in a decision of the House of Lords (Hammersmith and Fulham LBC v Monk (1991)), the question was whether a periodic tenancy held by two or more joint tenants was determinable by a valid notice to quit given by one joint tenant without the knowledge or consent of the other(s). The facts were not always precise and the House did attempt to reason from ordinary contractual principles. But the train of logic which had led from consideration of one precedent to another and which did suggest that one joint tenant could validly end a tenancy, was halted when reference was made to a statement to the contrary in Howson v Buxton (1928). This was considered and rejected as having ‘insufficient weight’. Other matters than purely logical principles have to be taken into account.
References are made occasionally within a judgment to the significance of logic, but generally within a wider context, for example, public policy, social concerns. In R v Gotts (1992), the House of Lords decided that duress was not available as a defense to a charge of attempted murder. Lord Jauncey asked: ‘Is there logic in affording the defense of duress to one who intends to kill but fails, and denying it to one who mistakenly kills intending only to injure? ... I can see no justification in logic, morality or law in affording to an attempted murderer the defense which is withheld from a murderer.’ It is of significance, however, that these remarks were preceded by reference to ‘the pervading climate of violence and terrorism’. Lord Jauncey was placing his reference to logic within a setting of social facts and desirable policies. Similarly, in R v R (1991), in which the House of Lords decided that a husband could be criminally liable for raping his wife, the matter was approached by means of a logical interpretation of the word ‘unlawful’ as used in s 1 of the Sexual Offences Act 1956, and s 1 of the Sexual Offences (Amendment) Act 1974. But it was preceded by an important observation on historical and social change: the status of women had changed in recent years out of all recognition, so that marriage is to be regarded now as a partnership of equals. Again, purely logical reasoning is taken into account together with interpretations of social realities.
The use of ‘reasoning by analogy’ which is prevalent in English law and which, if it is to be in accord with the rules of formal logic, demands the application of rules in exact style, illustrates a general departure from the strictness of those rules. Analogy arises from a process of arguing from similarity in known respects to similarity in other respects. ‘Running a country is like running a ship – the crew must obey the captain’ – here is an analogy involving perceived similarities. Cast in formal terms, argument by analogy may be stated thus: ‘X has certain elements, P, Q and R. Y also has elements P, Q and R. But X also has S. Therefore, Y has S.’ The analogy may be utilised so as to promote the understanding of a legal concept by indicating similarities between that concept and others that may be more familiar or more readily grasped. Argument by analogy has been used in English law to support, for example, the concept of the right of the State to interfere so as to prevent breaks in ‘the seamless web of the law’ in relation to breaches of conventional morality. The statement of Lord Simonds in Shaw v DPP (1962), suggesting the existence of a residual power in the courts of law which can be used to guard the State against attacks ‘which may be the more insidious because they are novel and unprepared for’, stems from an analogy between the defence of the state by its ‘guardians’ and the defence of morality by the ‘guardians of the law’. Specific criteria of formal rules relating to analogy (for example, ‘the greater the number of elements shared by X and Y, the stronger the conclusion’, or ‘as the dissimilar elements between X and Y increase, so the conclusion is weakened’) tend to be neglected in legal arguments based on analogy. Critics have pointed to some of the decisions in ‘causation cases’ (in particular, R v Jordan (1956) and R v Blaue (1975)) as having resulted from false analogies between the laws of physical causation and the type of causation perceived in the facts of these cases.
Some jurists have suggested that the unwillingness of English lawyers to follow rigidly the principles of formal logic may be a sure guarantee of continuing inconsistencies in the law. They point, for example, to the continuous ‘lease or licence’ saga in land law, exemplified by Facchini v Bryson (1952), Somma v Hazelhurst (1978), and Street v Mountford (1985), and argue that, had the concept of a lease been applied in strictly logical fashion to a consideration of the facts in these and similar cases, uncertainty and inconsistency might have been avoided. (The continuing inconsistencies may be perceived in Mehta v Royal Bank of Scotland (2000) and Bruton v Quadrant Housing Trust (1999).) Holmes’ comments on the question of consistency in law are pertinent: the law, he declares, is always approaching and never reaching consistency. ‘It will become consistent only when it ceases to grow.’ Pound reminds jurists that so called ‘scientific legal systems’, dominated by strictly logical reasoning, will result in the ‘petrifaction’ of law and the stifling of independent consideration of new problems and of ‘new phases of old problems’. Jurists who support the stance of Holmes and Pound have noted that the principles of formal logic were not responsible, for example, for the vital changes in the law of torts effected by the enunciation of the ‘neighbour principle’ in Donoghue v Stevenson (1932), or the important development of the ‘proximity test’ in Alcock and Others v Chief Constable of S Yorks Police (1991), or the articulation of the so called ‘Bolam test’ in relation to standards of skill to be expected from professional persons (Bolam v Friern Hospital (1957)).
Others argue that law based on systematic logical principles will enlarge control over the increasing diversity of legal situations. ‘It is like fishing with large nets rather than single lines.’ Cohen, in an examination of the place of logic in the law, suggests that this argument ignores the important differences between the natural sciences, in which logic is essential, and the legal order, which involves matters which are neither as definite nor as rigid as those of the physical order. The facts of the physical order allow highly exact description (for example, in quantitative terms); the facts of the legal order can almost always be disputed and disregarded as wrong in principle. ‘The specific gravity of mercury is 13.6’ is a statement which, in terms of its logical derivation, is on a different level from that occupied by the statement, ‘the court finds for defendant’. Cohen warns that, like some other useful instruments, logic can be ‘very dangerous and it requires great wisdom to use it properly ... A logical science of law can help us digest our legal material, but we must get good food before we can digest it’.
Dewey, jurist and logician, urges caution in the face of arguments advocating a more intensive application of syllogistic logic to legal questions. He notes that the syllogism implies that thought or reason has fixed forms of its own, ‘anterior to and independent of concrete subject matters and to which the latter have to be adapted whether or no’. This is to put the activity of rigid demonstration before that of search and discovery and to fall into the trap of accepting that for every possible case which might arise in the legal system, there is a fixed antecedent rule ‘already at hand’. The result is to produce what Pound terms ‘a mechanical jurisprudence’; it flatters the human longing for certainty. Thinking derived from a consideration of premises is, in itself, not to be condemned; the problem for the jurist is to find statements of general principle and particular fact which are worthy to serve as premises. Hence, Dewey concludes, either logic in legal thinking must be abandoned, or it must be logic relative to consequences rather than to antecedents – ‘a logic of prediction of probabilities rather than one of deduction of certainties’.
The difficulties of relying solely on formal logic in a search for solutions to problems of jurisprudence and to cases arising within the legal system are obvious. The danger may be, however, in the total rejection of logic as a tool in legal reasoning. In Cohen’s phrase, law without concepts or rational ideas, law that is not logical, is like pre-scientific medicine. Lord Devlin, too, warns: ‘The Common Law is tolerant of much illogicality especially on the surface; but no system of law can be workable if it has not got logic at the root of it’ (Hedley Byrne v Heller (1964)).
It is of interest to note, however, that attempts have been made to cast some aspects of legal thought and practice into patterns of strict logical (and algebraic) terminology. Kolm has presented his arguments for ‘pure distributive justice’, in the form of mathematical and formal logic. D’Amato has sought to convey the essence of Austin’s thought through the medium of cybernetic models reflecting the logical interconnections of Austin’s command theory of law. Judge Learned Hand (1872–1961) has summarised, in his ‘Hand formula’, a logical expression of the results of many American cases involving matters of basic negligence standards. He expresses his logical argument in algebraic terms. Let the standard of care be considered in terms of three variables: P (the probability of harm resulting to the claimant from any act or omission by the defendant); L (the gravity of the resulting harm or loss); B (the cost or burden of preventing the harm or loss). Then consider the expression B < PL, that is, in the words of Judge Posner, ‘If the burden to the injurer of avoiding the accident was less than the loss if the accident occurred, multiplied by the probability that it could occur, then the injurer is negligent’. The formula is explained and illustrated in Conway v O’Brien (1940).
The school of jurimetrics, which seeks to apply to legal problems the techniques of logic, an elementary calculus of legal probability and the utilisation of computer techniques, in the name of its slogan, ‘A scientific jurisprudence for a scientific age’, has had very limited success, particularly in handling the problems of the qualitative judgments which figure large in our law. In Posner’s words: ‘We have in law the blueprint or shadow of scientific reasoning, but no edifice.’ A jurisprudence in which scientific formal logic replaces legal reasoning would appear, at the moment, to lie, in Celan’s phrase, ‘well north of the future’.
The rules of formal logic may be found in Fundamentals of Logic, by Carney and Scheer. Bodenheimer considers law and scientific method in Chapter 17. Dewey examines the problem in ‘Logical method and law’ (1924) 10 Cornell LQR. Cohen’s article, ‘The place of logic in the law’, appears in Law and the Social Order. A lucid account of basic problems related to logic and the law is given by Levi in his essay, ‘The nature of judicial reasoning’, in Law and Philosophy, edited by Hook, and by Posner in ‘Law as logic, rules and science’, in The Problems of Jurisprudence.