Evaluative considerations and the nature of law

If you cannot tell what counts as a ‘vehicle’ without evaluative reasoning, then you cannot tell what law the Road Traffic Act makes merely by pointing out physical facts (such as that there were wheels on the chicken coop) and social facts (such as that Parliament used the word ‘vehicle’ in the Act). You cannot identify the law (that is, you cannot tell what legal rights and duties people have) without evaluative reasoning. That conclusion, if it is sound, seems to have important implications for the long-running debates in theory of law over the relation between fact and value in law, and over relations between law and morality. The conclusion seems to contradict one of the most provocative and controversial claims in the theory of law — the ‘sources thesis’, which Joseph Raz has stated as follows:

All law is source-based. A law is source-based if its existence and content can be identified by reference to social facts alone, without resort to any evaluative argument. (Raz (1994) at 194–5; see entry On the Nature of Law)

We can only decide whether the chicken coop was a ‘vehicle’ for the purpose of the Road Traffic Act by understanding the Act as pursuing a value, and by making an evaluative judgment as to whether the word ‘vehicle’ can be interpreted as applying to the chicken coop with due respect for the requirement of certainty in criminal liability. So we cannot identify the content of the law without resort to evaluative reasoning.

One way to rescue the sources thesis would be to say that judges need to make such evaluative judgments only in borderline cases for the application of legal language — and that they have discretion (that is, the law provides no standard that determines the matter) in those cases. But a clear case of a vehicle counts as a ‘vehicle’ for the purpose of the Road Traffic Act just because the evaluative considerations that justify the use of the word ‘vehicle’ in that context clearly support its application. The sources thesis seems to be contradicted even in the clearest cases of the application of a law stated in descriptive language. The content of such laws can only be identified on the basis of an evaluative judgment as to how the purposes of the law ought to be conceived. That form of evaluation, you may say, can only be carried out by engaging in the very same form of reasoning that, in Raz's theory, law excludes.

It is certainly true that, in order to decide what the sources have directed (and thereby, in Raz's terms, to identify the existence and content of a law), you need to understand the sense in which a word like ‘vehicle’ is used. But the existence and content of the offence can still be identified without first judging whether it ought to be an offence to do what Mr.Burr did, or whether there ought to be any offence at all of driving without pneumatic tires. The sources thesis articulates this important insight: in English law, there was no offence of driving without pneumatic tires, until Parliament acted to create it. Parliament might not have done so. Moreover, if the institutions of the law had not been prepared to treat the chicken coop as a vehicle, then because of that social fact, it would have been false (after a decision with precedential effect) to say that it was an offence to pull a chicken coop on iron wheels on the road. Because law is systematic (in the respect that the law gives legal institutions authority to identify the law), the courts' decisions determine legal rights and obligations. So, we might say, a law is source-based if its existence and content can be identified by reference to social facts alone, without resort to any evaluative argument (other than whatever evaluative argument may be needed to determine what the social facts are).

Raz's explanation of the nature of law is not undermined by the fact that evaluative judgments are necessary in order to identify the content of the law, as long as it is still possible for legal directives to have the exclusionary force that, in his theory of authority, they claim. The sources thesis is not undermined as long as the court in Garner v Burr can decide whether it is an offence to pull a chicken coop on wheels without pneumatic tires, without answering the question, ‘should it be an offence to use a vehicle without pneumatic tires?’ And indeed the court can do so. But it needs to ask the related question: ‘what is the relevant sense of “vehicle” for the purposes of this Act?’ It is what Parliament did that determines Lawrence Burr's liability; it may take evaluative reasoning to answer the question of social fact, ‘what did Parliament prohibit?’