Logic and normativity

What is made clear to the reader of [SvL08] already from the introduction, is that the role of logic in the investigation of human reasoning and cogni- tion should be reconsidered. Logic, and more specifically classical logic, was traditionally thought to be the basic normative system against which human

reasoning has to be judged. The paradoxical results of Wason’s selection task came to change this picture, leading to the hasty conclusion that logic needs to be divorced from cognition. In [SvL08] van Lambalgen and Stenning claim that, after a careful examination of the assumptions which led logic and cognition to be divorced, we can bring the two back together as they should be.

Specifically, van Lambalgen and Stenning object to Wason’s conclusion that reasoning is rational if it follows rules from a given and fixed set since, according to them, this view implies that logic should be viewed as irrelevant for cognition. The view that they support instead, is that reasoning is everywhere and some- times it is not consciously processed but automatic. What their investigations have led them realize is that people may some times reason in ways which are inconsistent with their chosen interpretation which means that evidence for the interpretation which is independent of the performance is necessary when one uses a particular interpretation to explain performance.

Thus, van Lambalgen and Stenning claim that we should reconsider the role logic plays in human reasoning and try to use logic in the correct way, rather than abandoning it. One of the main roles of their work is to present new ways towards the understanding of reasoning in which logic can still be thought of as normative,but [SvL08, p. 11]:

norms apply to instances of reasoning only after the interpretation of the (logical and non-logical) expressions in the argument has been fixed, and, furthermore, there are in general multiple natural options for such inter- pretations, even for interpreting the logical expressions. Thus, the reason- ing process inevitably involves also steps aimed at fixing an interpretation; once this has been achieved, the norms governing logical reasoning are also determined.

The foundations of their investigations can be tracked back in Husserl, for who we should reserve a couple of paragraphs here. Let’s go back to one of the questions posed in the previous section: Is there a definite and exhaustive list of rules which define rationality? In other words, are there unassailable and objective rules that define rationality? If we assume that logic provides such rules we have to give a justification of why we take these rules to be unassailable and objective. Husserl, in his Logische Untersuchungen, made a completely innovative suggestion: logic should be viewed not as a normative but as a

theoreticaldiscipline. By that he meant that logic as a theoretical discipline can, via theoretical statements of the type ‘only such and such arguments preserve truth’ and in combination with normative arguments of the type ‘truth is good’, derive the conclusion that ‘only such and such arguments are good’. Thus, truth is ana priori concept and theories such as logic can determine only which rules are valid within the theory.

In the above picture normativity still has a central role. Logic consists of laws which are indeed unassailable and objective, but not in the same sense as before; logical laws are not providing absolutely valid norms, they are just providing valid norms relative to a particular domain and thus they are unassailable only as mathematical consequences of the structure of the domain studied.

In a similar way, van Lambalgen and Stenning claim that normativity plays a role in reasoning about reasoning tasks, but normativity enters the picture via an appropriate formal theory only after a stipulation of the meaning of the reasoning task has been given by following some a priori constitutive norms. This distinction will become obvious in the next sections where we will talk about the processes of reasoningto and from an interpretation and about the distinction betweenregulative andconstitutive norms.

Finally, we should say that van Lambalgen and Stenning view logic ‘as the mathematics of information systems, of which people are one kind’ [SvL08, p. 14] and they suggest that this view

helps in that it makes clear from the start that one’s choice is never between “doing psychology” and “doing logic”. Understanding reasoning is always going to require both, simply because science does not proceed far without conceptual and mathematical apparatus. [SvL08, p. 14]

We see that van Lambalgen and Stenning believe that logic and psychology are two tightly connected disciplines. We could situate their view in the ‘natu- ralized epistemology’ category that was discussed in section1.1. Normativity is still in the picture, even though in a new form, and empirical scientific investi- gation is considered as the basic strategy for arriving at the right understanding of reasoning and rationality. Therefore, the ‘psychologism’ of van Lambalgen and Stenning,

requires an account of how logic in its modern guise [multiplicity of logics] as a mathematical system is related to psychology in its modern guise as experimental science. [SvL08, p. 15]

In the following section, we will see how this new view of logical reasoning sketched here can be used in the psychology of reasoning according always to the theory which van Lambalgen and Stenning develop in [SvL08].