Theoretical and methodological pluralists aim at justifying the co-existence of a plurality of acceptable theories and of acceptable methods by appealing to reasons. Why should we hold pluralist views? And what limits should we give to pluralism? This paper proposes a new argument in favour of pluralism in economics and then discusses the limits of pluralism.

The argument is the following. On the one hand, if we have no assurance that a particular scientific theory/method is the “good” one, it is better to allow for a variety of them, so as to maximise the chance of finding the “good” one and to minimize the probability to stick to a “bad” one. On the other hand, if we happen to know which theory/method is the good one, this is nevertheless not a sufficient reason to ban concurrent theories/methods, for the latter may help us refine the established scientific practice and bring it closer to truth. I argue that this argument has several important virtues, especially its humility, its tolerance, its pragmatism and its potential appeal to both mainstream and non-mainstream economists. However, one could wonder what the limits of such pluralism are. How can one avoid both dogmatism and relativism?

First, I argue that a practice cannot count as scientific in virtue of the fact that it happens to be the dominant practice, i.e. that it is the most widespread within universities and research centres. Second, I defend the more demanding claim that a scientific practice can be included within the pluralist scientific realm if there exists a community of practitioners that share this practice and if this community is able to justify its practice to other communities with reasons they can accept.

On the one hand, the existence of a community guarantees internal peer-criticism, which is an important condition of scientific rigour and is a first check on pluralism. On the other hand, justifications must appeal to reasons that scientists of a particular community have for choosing to practice science in a certain way. Acceptable reasons include the formal rigour of the approach, the fruitfulness of the approach, the ability to explain phenomena considered crucial to reality, etc.

My claims rely on two assumptions. First, scientists must be reasonable, i.e. they must be ready to listen to others' reasons for doing science and possibly to accept them if this is justified. Second, scientists should have a minimal shared understanding of science, that is, some common values (epistemic values), such as rigour, consistency, commitment to truth, etc. Appeal to such values is what makes a practice potentially justifiable to other scientific communities.

These claims have several corollaries. First, this is an invitation to dialogue. Each community must justify its practice to others while trying to understand and evaluate others' reasons. Second, defending pluralism does not mean that everyone should be a pluralist. Individual scientists can remain attached to a specific community, while accepting that other ways of doing science are also acceptable. Third, there is still a large space for disagreement. Scientists just need to agree on the core reasons that drive scientific inquiry, i.e. that motivate the choice of a peculiar practice, not on the particular content or methods of each other's scientific inquiry.