MRS. ALVING. Well, I seem to find explanation and confirmation of all sorts of things I myself have been thinking. (1.166)
Mrs. Alving's slow and gradual change of perspective has come about through a process of her observation, thinking, and reading progressive literature. The appearance of Oswald frees her to move further away from social conformity.
MANDERS. In his youth he overflowed with the joy of life – (1.294)
It's ironic that Manders first introduces this key phrase: "joy of life." He is admiringly describing Captain Alving. The "joy of life" is all about freedom, openness, and personal choice – everything that Manders, as a representative of the Norwegian status quo – is pitted against.
OSWALD. Well, you may take their word for it. They know what they are talking about! [Presses has hands to his head.] Oh! that that great, free, glorious life out there should be defiled in such a way! (1.342)
At this point in the play, Oswald is tortured by the thought that his own involvement at "that great, free, glorious life out there" has brought about his ruin. Little does he know that his father could have been one of the men he describes coming down to Paris to "slum it" among artists.
MRS. ALVING. But when the last insult was added; when my own servant-maid – ; then I swore to myself: This shall come to an end! And so I took the reins into my own hand – the whole control – over him and everything else. (1.411)
Mrs. Alving describes the iron grasp she had on her wayward husband. As a man with a personality drawn to freedom and pleasure, he must have resented her. In turn, she must have felt like a warden.
MRS. ALVING. Well, I can't help it; I must have done with all this constraint and insincerity. I can endure it no longer. I must work my way out to freedom. (2.44)
In Act 2, Mrs. Alving is still caught between her proper Norwegian upbringing and her desire for openness and honesty. She's working her way from Pastor Manders's approach to life and towards that of her son.
OSWALD. Then of course he had to admit that he was on the wrong track; and so I learned the truth – the incomprehensible truth! I ought not to have taken part with my comrades in that lighthearted, glorious life of theirs. It had been too much for my strength. So I had brought it upon myself! (2.276)
It's hard to know exactly what Oswald is referring to when he talks about "that lighthearted, glorious life of theirs." Free love? Alcohol? Drugs? Whatever he means, he doesn't condemn the behavior, only his own weakness.
OSWALD. – then it flashed upon me that in her lay my salvation; for I saw that she was full of the joy of life. (2.360)
Oswald sees Regina as the instrument of his freedom. She's too vivacious and strong-willed to let him live as an invalid for long.
MRS. ALVING. [Starts.] The joy of life? Can there be salvation in that? (2.361)
Mrs. Alving still thinks that "joy of life" may be something sinful and is surprised that Oswald associates it with the religious idea of salvation. Of course she doesn't know yet that when Oswald says "salvation," he actually means "assisted suicide." Nevertheless she is listening.
MRS. ALVING. [Looks steadily at him.] Do you think that is what would happen? OSWALD. I know it. You may live the same life here as there, and yet it won't be the same life. MRS. ALVING. [Who has been listening eagerly, rises, her eyes big with thought, and says:] Now I see the sequence of things. (2.384-386)
As Mrs. Alving begins to understand her husband's need for freedom and joy, she also begins to understand her own mistakes. It's a big moment for her. Yet it's not a dramatic explosion. It's a subtle, internalized click in the character's mind. Ibsen is full of turning points like this.
MRS. ALVING. Yes, now I can, Oswald. A little while ago you spoke of the joy of life; and at that word a new light burst for me over my life and everything connected with it. (3.108)
As Mrs. Alving explains her discovery to Oswald, she's full of hope that her new understanding – and her confession – will solve her problems. But other, worse complications haven't even been revealed. The play is like a series of doors opened – only to find another closed door.