Section 2.2 of the SEP article on modal epistemology differentiates possibility-first from necessity-first systems. Per modal logic, one can take these as metaphysical readings of the order-of-definition for the diamond and box operators. By analogy, then, one can speak of deontic systems as permission-first or obligation-first, say.

Now, to my knowledge, we might bracket Aquinas' ethics in terms of two imperatives (I say "might" in part to indicate that such bracketing is amiss):

  1. A trivial imperative, "Do good and avoid evil." (The linked SEP article tries to paint a nontriviality picture, here, but the whole article is fairly presumptuous and so anyway, I think the picture is not well-painted.)
  2. An apex imperative, "Undergo the beatific vision."

However, for other reasons, (2) is not well-stated. For example, if the divine nature is the one that provides the visio beatifico, and that nature is exempt from any external (or perhaps even internal) commands, or is at least exempt from nontrivial commands (so to say), then in revising (2) we are motivated to try out, "Make oneself worthy of the vision" (2') instead. Then, for the same reason that the first formulation was wrong, but in a different direction, (2') needs to be recast as, "Accept the vision if the divine nature gives it to you" (2'').

Unfortunately, that's still wrong: once the divine nature has displayed itself to a creature so fully, "the deal is done" and there is nothing to accept or reject (for one cannot, while already undergoing the vision, reject it). So (2'') might have to be more like, "Accept the grace that will make you worthy of the vision." Now, in this case, we do have an obligation—but it is one effectively relative to a supererogatory condition for the divine nature, i.e. its decision to impart (impute!) grace to this or that agent. It is, if you will, a deduction of an obligation from a supererogation: since it would be supererogatorily good for the divine nature to impart grace, it is obligatory for possible recipients of grace to properly dispose themselves towards the prior, divine supererogation.

Does this mean that Aquinas' implicit deontic logic, modulo (if anachronistically) modern technical sensibilities, can be taken for a supererogation-first system? The SEP article on deontic logic mentions one researcher (one of the article's authors) having a way to take a "least that can be done" operator to inform our understanding of a "it is supererogatory that" operator, in an ensemble of more typical such operators, so I would think (though I don't exactly recall from earlier reading) that the overall such system might allow for starting from a supererogation operator and then formulating the rest of the operators as modifications thereof.

1 Answer 1


First, let's clarify that while Aquinas' ethics certainly involve elements of supererogation (acts that go beyond duty or obligation), it's crucial to understand that they're grounded in a broader context of virtue ethics and natural law. Aquinas isn't simply saying, "Do good things if you feel like it." He's making claims about the inherent nature of morality and our obligations within that framework.

Your question seems to hinge on whether Aquinas' deontic logic, given modern sensibilities, might be interpreted as a supererogation-first system. Let's not forget that Aquinas was a product of his time, and the concepts we're applying here are distinctly modern.

As to the idea of "deducing an obligation from a supererogation," it's a fascinating thought, but I think it risks oversimplifying Aquinas' thought. The beatific vision, as Aquinas presents it, isn't a bonus round in the game of life—it's the ultimate end goal of human existence.

The idea of supererogation as the first principle seems to imply that morality is optional, or at the very least, that it's a matter of going above and beyond some baseline. This isn't quite in line with Aquinas' thinking. For him, the moral law is written into the fabric of reality itself, and our duty is to align ourselves with that law.

So, while there's certainly room to discuss the role of supererogation in Aquinas' ethics, I wouldn't go so far as to call it a supererogation-first system. Rather, it's a system that recognizes supererogation within a broader framework of obligation and virtue.

  • I don't know if it was so in Aquinas' time (maybe he's the one who came up with the idea, even), but the RCC's theory is that the only entirely permanent sin is trivially permanent, as an until-death rejection of grace. Does this imply a duty to accept grace, an obligation to respond "appropriately" to a supererogation? I also thought it was odd how Dante seemed to say somewhere, "God ought to punish unless He forgives," which can be converted into, "God ought to punish or forgive." If Aquinas' ethics were implicitly S-first, not OB-first, it would be so on God's side of things, then, maybe. Aug 1 at 1:10

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