"To be sure" in "Emma"

And here are many of the appearances of "to be sure" in Austen's Emma. I really wonder about how to interpret this expression. It's quite slippery. Suggestions?

To be sure

            "That may be, and I may have seen him fifty times, but without having any idea of his name. A young farmer, whether on horseback or on foot, is the very last sort of person to raise my curiosity. The yeomanry are precisely the order of people with whom I feel I can have nothing to do. A degree or two lower, and a creditable appearance might interest me; I might hope to be useful to their families in some way or other. But a farmer can need none of my help, and is, therefore, in one sense, as much above my notice as in every other he is below it."

            "To be sure. Oh yes! It is not likely you should ever have observed him; but he knows you very well indeed—I mean by sight."

*

            "You could not have visited me!" she cried, looking aghast. "No, to be sure you could not; but I never thought of that before. That would have been too dreadful!—What an escape!—Dear Miss Woodhouse, I would not give up the pleasure and honour of being intimate with you for any thing in the world."

*

            "Then she is a greater simpleton than I ever believed her. What is the foolish girl about?"

            "Oh! to be sure," cried Emma, "it is always incomprehensible to a man that a woman should ever refuse an offer of marriage. A man always imagines a woman to be ready for any body who asks her."

*

            "Upon my word, Emma, to hear you abusing the reason you have, is almost enough to make me think so too. Better be without sense, than misapply it as you do."

            "To be sure!" cried she playfully. "I know that is the feeling of you all. I know that such a girl as Harriet is exactly what every man delights in—what at once bewitches his senses and satisfies his judgment. Oh! Harriet may pick and chuse. Were you, yourself, ever to marry, she is the very woman for you. And is she, at seventeen, just entering into life, just beginning to be known, to be wondered at because she does not accept the first offer she receives? No—pray let her have time to look about her."

*

            The picture!—How eager he had been about the picture!—and the charade!—and an hundred other circumstances;—how clearly they had seemed to point at Harriet. To be sure, the charade, with its "ready wit"—but then the "soft eyes"—in fact it suited neither; it was a jumble without taste or truth. Who could have seen through such thick-headed nonsense?

*

            Miss Bates, deceived by the mock ceremony of her manner, did not immediately catch her meaning; but, when it burst on her, it could not anger, though a slight blush shewed that it could pain her.

            "Ah!—well—to be sure. Yes, I see what she means, (turning to Mr. Knightley,) and I will try to hold my tongue. I must make myself very disagreeable, or she would not have said such a thing to an old friend."

*

            "Harriet!" cried Emma, collecting herself resolutely—"Let us understand each other now, without the possibility of farther mistake. Are you speaking of—Mr. Knightley?"

            "To be sure I am. I never could have an idea of any body else—and so I thought you knew. When we talked about him, it was as clear as possible."