"Ratification" is defined as "the act or process of ratifying something (such as a treaty or amendment) : formal confirmation or sanction". Self-ratification, then, is assigning validity to one's self. (My use of the term "self-ratification" follows philosophical usage in analysis of causal decision theory)
At first this seems like a trivial condition. It is, indeed, easy to write silly sentences such as "This sentence is true and also the sky is green", which are self-ratifying. However, self-ratification combined with other ontological and epistemic coherence conditions is a much less trivial condition, which I believe to be quite important for philosophical theory-development and criticism.
I will walk through some examples.
Causal decision theory
Formal studies of causal decision theory run into a problem with self-ratification. Suppose some agent A is deciding between two actions, L and R. Suppose the agent may randomize their action, and that their payoff equals their believed probability that they take the action other than the one they actually take. (For example, if the agent takes action L with 40% probability and actually takes action R, the agent's payoff is 0.4)
If the agent believes they will take action L with 30% probability, then, if they are a causal decision theorist, they will take action L with 100% probability, because that leads to 0.7 payoff instead of 0.3 payoff. But, if they do so, this invalidates their original belief that they will take action L with 30% probability. Thus, the agent's belief that they will take action L with 30% probability is not self-ratifying: the fact of the agent having this belief leads to the conclusion that they take action L with 100% probability, not 30%, which contradicts the original belief.
The only self-ratifying belief is that the agent will take each action with 50% probability; this way, both actions yield equal expected utility, and so a policy 50/50 randomization is compatible with causal decision theory, and this policy ratifies the original belief.
(This example is due to Robin Hanson's "Uncommon Priors Require Origin Disputes".)
Suppose Oscar and Peter are brothers. Oscar is more optimistic than Peter. Oscar comes to believe that the reason he is more optimistic is due to inheriting a gene that inflates beliefs about positive outcomes, whereas Peter did not inherit this same gene.
Oscar's belief-set is now not self-ratifying. He believes the cause of his belief that things will go well to be a random gene, not correlation with reality. This means that, according to his own beliefs, his optimism is untrustworthy.
Low-power psychological theories
Suppose a psychological researcher, Beth, believes that humans are reinforcement-learning stimulus-response machines, and that such machines are incapable of reasoning about representations of the world. She presents a logical specification of stimulus-response machines that she believes applies to all humans. (For similar real-world theories, see: Behaviorism, Associationism, Perceptual Control Theory)
However, a logical implication of Beth's beliefs is that she herself is a stimulus-response machine, and incapable of reasoning about world-representations. Thus, she cannot consistently believe that her specification of stimulus-response machines is likely to be an accurate, logically coherent representation of humans. Her belief-set, then, fails to self-ratify, on the basis that it assigns to herself a level of cognitive power insufficient to come to know that her belief-set is true.
Moral realism and value drift
Suppose a moral theorist, Valerie, believes:
- Societies' moral beliefs across history follow a random walk, not directed anywhere.
- Her own moral beliefs, for the most part, follow society's beliefs.
- There is a true morality which is stable and unchanging.
- Almost all historical societies' moral beliefs are terribly, terribly false.
From these it follows that, absent further evidence, the moral beliefs of Valerie's society should not be expected to be more accurate (according to estimation of the objective morality that Valerie believes exists) than the average moral beliefs across historical societies, since there is no moral progress in expectation. However, this implies that the moral beliefs of her own society are likely to be terribly, terribly false. Therefore, Valerie's adoption of her society's beliefs would imply that her own moral beliefs are likely to be terribly, terrible false: a failure of self-ratification.
Trust without honesty
Suppose Larry is a blogger who reads other blogs. Suppose Larry believes:
- The things he reads in other blogs are, for the most part, true (~90% likely to be correct).
- He's pretty much the same as other bloggers; there is a great degree of subjunctive dependence between his own behavior and other bloggers' behaviors (including their past behaviors).
Due to the first belief, he concludes that lying in his own blog is fine, as there's enough honesty out there that some additional lies won't pose a large problem. So he starts believing that he will lie and therefore his own blog will contain mostly falsehoods (~90%).
However, an implication of his similarity to other bloggers is that other bloggers will reason similarly, and lie in their own blog posts. Since this applies to past behavior as well, a further implication is that the things he reads in other blogs are, for the most part, false. Thus the belief-set, and his argument for lying, fail to self-ratify.
(I presented a similar example in "Is Requires Ought".)
Suppose Phyllis believes that the physical world exists, but that minds don't exist. That is, there are not entities that are capable of observation, thought, etc. (This is a rather simple, naive formulation of eliminative materialism)
Her reason for this belief is that she has studied physics, and believes that physics is sufficient to explain everything, such that there is no reason to additionally posit the existence of minds.
However, if she were arguing for the accuracy of her beliefs about physics, she would have difficulty arguing except in terms of e.g. physicists making and communicating observations, theorists having logical thoughts, her reading and understanding physics books, etc.
Thus, her belief that minds don't exist fails to self-ratify. It would imply that she lacks evidential basis for belief in the accuracy of physics. (On the other hand, she may be able to make up for this by coming up with a non-mentalistic account for how physics can come to be "known", though this is difficult, as it is not clear what there is that could possibly have knowledge. Additionally, she could believe that minds exist but are somehow "not fundamental", in that they are determined by physics; however, specifying how they are determined by physics requires assuming they exist at all and have properties in the first place.)
I hope the basic picture is clear by now. Agents have beliefs, and some of these beliefs imply beliefs about the trustworthiness of their own beliefs, primarily due to the historical origins of the beliefs (e.g. psychology, society, history). When the belief-set implies that it itself is untrustworthy (being likely to be wrong), there is a failure of self-ratification. Thus, self-ratification, rather than being a trivial condition, is quite nontrivial when combined with other coherence conditions.
Why would self-ratification be important? Simply put, a non-self-ratifying belief set cannot be trustworthy; if it were trustworthy then it would be untrustworthy, which shows untrustworthiness by contradiction. Thus, self-ratification points to a rich set of philosophical coherence conditions that may be neglected if one is only paying attention to surface-level features such as logical consistency.
Self-ratification as a philosophical coherence condition points at naturalized epistemology being an essential philosophical achievement. While epistemology may possibly start non-naturalized, as it gains self-consciousness of the fact of its embeddedness in a natural world, such self-consciousness imposes additional self-ratification constraints.
Using self-ratification in practice often requires flips between treating one's self as a subject and as an object. This kind of dual self-consciousness is quite interesting and is a rich source of updates to both self-as-subject beliefs and self-as-object beliefs.
Taking coherence conditions including self-ratification to be the only objective conditions of epistemic justification is a coherentist theory of justification; note that coherentists need not believe that all "justified" belief-sets are likely to be true (and indeed, such a belief would be difficult to hold given the possibility of coherent belief-sets very different from one's own and from each other).
Appendix: Proof by contradiction is consistent with self-ratification
There is a possible misinterpretation of self-ratification that says: "You cannot assume a belief to be true in the course of refuting it; the assumption would then fail to self-ratify".
Classical logic permits proof-by-contradiction, indicating that this interpretation is wrong. The thing that a proof by contradiction does is show that some other belief-set (not the belief-set held by the arguer) fails to self-ratify (and indeed, self-invalidates). If the arguer actually believed in the belief-set that they are showing to be self-invalidating, then, indeed, that would be a self-ratification problem for the arguer. However, the arguer's belief is that some proposition P implies not-P, not that P is true, so this does not present a self-ratification problem.