I declare, . . .

[shootingstar]

. . .
MRS. GIBBS: All told, you won't get more'n three hours' sleep. Frank Gibbs, I don't know what's goin' to become of you. I do wish I could get you to go away someplace and take a rest. I think it would do you good.
MRS. WEBB: Emileeee! Time to get up! Wally! Seven o'clock!
MRS. GIBBS: I declare, you got to speak to George. Seems like something's come over him lately. He's no help to me at all. I can't even get him to cut me some wood.
DR. GIBBS: Washing and drying his hands at the sink. MRS. GIBBS is busy at the stove. Is he sassy to you?
MRS GIBBS: No. He just whines! All he thinks about is that baseball - George! Rebecca! You'll be late for school.
. . .
(Thornton Wilder, Our Town, Act I)

What does I declare, . . . mean in this sentence? Please mind the comma there.

 

[Barque]

It's a sort of exclamation. You can read it as "I really do think that" or "I strongly believe that", depending on where it's used. It's an old-fashioned term nowadays though it might survive in some places.

 

[5jj]

It's a sort of exclamation.

I agree.

You can read it as "I really do think that" or "I strongly believe that",

I don't agree. It's as meaningless as Goodness me!