The essay in "The Seas of Language" that I think actually answers your post is "Wittgenstein on Necessity: Some Reflections". He discredits a wholly logical/mathematical approach as if to say that logical or mathematical necessity can be used to bridge communication differences (e.g., Dick's approach), while at the same time discrediting Luis' approach that there is "nothing to truth beyond our acknowledgement of truth". He considers this approach totally implausible.
Rather, like myself, he suggests that "global internalism is required as a premiss to take us from the epistemology of rules to their metaphysical standing". Where have we heard that before? (applause: thank you, thank you). Anyway, getting back to Dummett's answer:
"The conventionalists were led astray by the example of the founders of modern logic into concentrating on the notion of logical or analytic truth (his emphasis and throughout), whereas precisely what they needed to fasten on was that of deductive consequence, which it is helpful to think of in terms of the metaphor of patterns. Even the simplest judgement imposes a pattern upon reality, a pattern in common between the variegated circumstances which would verify it. To make the judgement requires us not merely to attend passively to the relevant circumstances, but, deploying the concepts involved in the judgement, to discern the appropriate pattern in them. A deductive step brings about a small shift in the pattern apprehended; a series of such steps brings us to discern a pattern previously quite unexpected. When the step requires two premisses, we first superimpose two patterns on one another, to extract a third. The discerntment of a new pattern is not merely compatible with, but requires, a recognition that that in which it is discerned has not itself changed; it is this which renders the deductive argument valid, while the novelty of the pattern represents the epistemic advance. The rules of inference which govern the deductive transitions themselves consist in the recognition of a pattern; not of a pattern in reality, but of one in a set of judgements, which mediates the passage from the discernment of one simple or complex pattern in reality to the discernment of another. Certainly our ability to discern patterns depends upon the stock of concepts available to us, which we acquire with our language and to which to a very limited extent we ourselves add; be we do not impose the patterns, but discern them, and the capacity of one pattern to be transformed into another is intrinsic, not created by our ability to perform the transformation."
So, what Dummett is saying is that we are not relying on logical necessity to describe and communicate reality (e.g., Dick's approach), but rather we are relying on pattern discernment which is partly constrained within our language and the concepts available to us. Hence, this is the best we can do with our limitations. We can make inferences, but no further. However, we are constrained to make this effort. That is, Dummett maintains that saying there is nothing to truth beyond our acknowledgement of truth is totally implausible (which is how I understand Luis' position, called extreme internalism).
In the case of me and Paul, the best we can do then, is to go through the process of understanding each other's language and what constraints we are placing on reality (e.g., logico-mathematical necessity, inability to know, etc), and hopefully come to a point to where we think we understand each other. There is no definite way to know.
Warm regards, Harv