The thing that puzzles me is how do we know that two people are thinking the same way?

We've all heard of the question where my ''blue'' could be enitrely different from your version of ''blue''. Yet, we somehow (miraculously) agree on the proposition: the sky is ''blue''.

Taking this line of thought only a little further how do we know we're all thinking the same way? We could all have individual ways of thinking, entirely different from each other, yet we may (miraculously) come to the same conclusion.

I wonder... — TheMadFool

Suppose you and I have a hunch we're thinking of the same grocery store in town, but we're not sure. We might go there together and look. When each of us declares that he's thinking of a route to the place, we might check in a similar way whether it's the same route we have in mind. Or the same kind of endive or cheese.... Or the same philosophical view on justice or truth...

What is a "version of blue"? Which blue do you have in mind -- the blue of the sky right now out there, or the blue of that big old Buick on the corner? Our "versions of colors" appear determined at least in part "outside our heads", as it's sometimes put.

Our "versions of thoughts" seem determined at least in part in the same place. In many cases my actions give you a fair idea what I believe about the world, what propositions I'm disposed to assent to or deny, on the basis of my action in the world. In some of those cases, the actions in question are speech acts. We can determine whether we have similar thoughts about justice, truth, or works of fiction by speaking together about justice, truth, or works of fiction, for as long as it takes to get satisfied on this account. In one sense there is little difference between what we "think" about a subject or a proposition, and what we "say" (or would say) about the same subject or proposition when speaking sincerely. In another sense there may be differences. For instance: I may consistently and sincerely assert that some proposition is true, while consistently acting in some other way, without speech, as if it were false. In such cases it may seem my speech is inconsistent with my other action. You might do me the favor of bringing the discrepancy to my attention, and invite me to account for it.