It is fairly clear that, when I say “I like this” and “This is good,” I do not mean the same thing. Even though I should reverse the position of the two relata in my expression of the former proposition and state the non-symmetrical relation intended in the equivalent form, “This is liked by me” unidiomatically or, in good English, by “This pleases me,” the meaning of what I assert would not be logically equivalent to “This is good.” True, it is certain that, if I actually believe the latter, I also believe the former; this must please me in some way: I approve of it. Here, however, we have only one-sided implication, not equivalence; B implies A, but A does not imply B.