A priori judgments and the argument from design

Conclusions

At the outset of this discussion, I undertook to present an argument from design which would follow Swinburne's example in making use of a priori judgments, while avoiding some of the objections which have been posed in response to his treatment of these issues. So we need to ask: how does this approach to the question of design compare with Swinburne's?

Swinburne argues that a chaotic world is a priori more likely than an ordered world: this consideration provides one central reason, on his account, for giving an explanation of some sort for the world's regularity. The other central argument he advances for this claim is the argument from analogy (in terms of the coins) which we noted earlier. The approach I have taken offers an alternative route to this same conclusion. In particular, it substitutes the simpler a priori judgments recorded in (i) and (ii) for the rather difficult and contentious claim that chaos is a priori more likely than order. In place of this claim, I have offered the judgment that order, or recurrence, is more likely given the activity of a common source or common kind of source than otherwise: this proposal does not commit us to a view either way on the question of whether order is a priori likely per se. Moreover, in place of Swinburne's analogical argument, I have offered an a priori approach, with the advantages I have noted.

Given that recurrence is to be explained, we might ask: why offer an explanation in terms of design? On this point, Swinburne argues, for instance, that no other explanation of temporal regularity is even possible a priori. Again, the a priori principles which I have used, in (iv) and (v), may be less ambitious, but at the same time more persuasive. In support of this same idea, Swinburne also cites various ideas to do with the predictive power of the idea of design. I have tried to bring out the role of this sort of consideration in terms of my principle (v). Principle (iv) has no place in Swinburne's account, in view of his reliance on the principle of simplicity as a measure of prior probability.

Lastly, we may ask: if we are to cite a designer, are there reasons for attributing to this agent more powers than are needed for the production of the effect to be explained? On this point, Swinburne cites the principle of simplicity. Again, my approach avoids what has proved to be a relatively controversial judgment about the nature of a priori probabilities, offering in place of the principle of simplicity the less ambitious principle recorded in (iii). At this point, I have moreover inverted the logical sequence of Swinburne's argument: it seems to me that, in the ways I have indicated, it is helpful to consider the extent of the powers of the source of recurrence before addressing the question of design.

In these various ways, I hope I have made good my undertaking to present an argument which avoids some of the controversy surrounding the particular measures of a priori probability which figure in Swinburne's argument. Moreover, I hope that this approach provides an indication of how a priori judgments may function in a relatively unproblematic way within an argument from design, in so far as (i)–(v) are all rather modest proposals. In sum, the argument I have presented is distinguished by its explicit use of the a priori judgments recorded in (i)–(v), by its attempt to buttress in this fashion analogical forms of argument, and by the logical role it gives to the idea that the source of regularity possesses more powers than are required for the production of this effect.

Lastly, we might ask: how persuasive is this argument? Of course, the cogency of the idea of design depends upon the balance of debate in other areas of the philosophy of religion, especially upon our ability to provide some account of the existence of evil. In this paper, I have been concerned to argue simply that recurrence by kind provides evidence for design: I have not addressed the question of whether other features of the world provide good evidence against the idea of (benevolent) design. However, if we confine our attention to this one phenomenon, there is it seems to me good evidence for the idea of design, (i) and (ii) suggest that recurrence surely calls for some explanation; (iii), together with the existence in nature of statistical irregularities, suggests that whatever provides this explanation could have brought about other effects besides; and design seems the only clear explanation of why this effect should have been brought about, if (as I have argued) analogies drawn from vegetable and animal reproduction fail, and if we cannot explain the effect satisfactorily by reference to the conditions of observation. Moreover, I have argued that there are reasons for supposing that the probability a priori of design is relatively high in relation to the probability a priori of any rival hypothesis of equivalent predictive power. In brief, this is because the design hypothesis (unlike the hypothesis of theism) can cite an agent of relatively indeterminate power in order to account for the phenomenon to be explained. In this regard, it is less ‘precisely defined’ than any rival hypothesis of equivalent predictive power. If all of this is so, then as philosophers from early times have supposed, temporal regularity provides the basis for a powerful argument in favour of design. It remains true, of course, that its import can be judged in full only when we have taken into account the relevance of other phenomena, many of which are apparently less favourable to the idea of design.