[quote="Tennis77, post:1, topic:270962"]
If Protestants believe in Sola Scriptora, then how can this teaching change, because the Bible certainly hasn't changed, which is the only authority that they recognize.
There's the rub. If I plop the Bible in front of you and say that you must extract every rule about every life possibility from there, you'd be hard-pressed to make sense of it.
Since Protestants claim that a book is the ONLY authority, then anyone reading that book can interpret some passages differently. And since there is no visible authority, who's to say that one interpretation is correct?
If given enough time, just about every non-Catholic Christian group will hold a belief that seems astonishing to Catholics. You bring up the case of contraception, which seemed to have unanimity before 1930. Well, what about abortion, which every Christian condemned until a few decades ago? What about so-called "gay marriage," which any Christian would have rebuked (or probably laughed at) in the 1940s?
Those things are all clearly anti-Christian. But even if forbidden by the Bible itself (such as homosexual acts), you'll find someone who claims that it's now OK!
So I don't have a great answer for your original question ... I'm just saying that it's not a surprise when you've rejected the very authority given by Christ: His Church.