The phrase "a relevant proposition" is correct and usable in written English.
It can be used when discussing ideas, arguments, or statements that are pertinent to a particular topic or context.
Example: "In our debate, I presented a relevant proposition that addressed the core issues at hand."
Alternatives: "an applicable statement" or "a pertinent assertion".
One avenue to knowledge in this case lies in the ability of the agent to provide a proof of the relevant proposition.
Since, according to RTM, to think a certain thought is just to token a representation in the head that expresses the relevant proposition, the ability to token certain representations is systematically connected to the ability to token certain others.
When a thinker in the good case comes to know that there is blood on the knife in virtue of having a visual experience as of blood on the knife, the relevant proposition becomes part of his total evidence.
In contrast, when a thinker in the bad case is caused by the Demon to undergo the same experience (or at least, an experience that is qualitatively indistinguishable) and arrives at the same belief, the relevant proposition is not part of his total evidence, for the relevant proposition is not true and hence not known.
We might also think that knowledge-how can involve merely justified belief in the relevant proposition, as long as knowledge how can be Gettiered (as Poston (2009) argues).
A more plausible requirement is that a priori knowledge and justification be independent of all experience beyond what is needed to grasp the relevant concepts involved in the relevant proposition (see below, sec. 4).
Davidson's idea is that a source can supply justification only if it has propositional content, so that the source is assessable as accurate or inaccurate, depending on whether the relevant proposition is true.
Proponents of this sort of view think of propositions as structured: as having constituents which include the meanings of the expressions which make up the sentence expressing the relevant proposition.
In theory, the two readings can be distinguished by checking whether a particular reading is about the speaker's subjective knowledge or is about how the relevant proposition will/would come about independently of speaker perception and judgment.
However, she must also have additional experience beyond that in order to determine whether the relevant proposition is true or false, or be aware of the testimony of someone who has had the requisite additional experience.
