[Siena Dreaming]

we must insist that sinlessness and infallibility are two separate issues and do not have to coincide

I believe they do.

The only person in history who was not liable to error was Christ and that is because He did not have a sin nature.

Those who have a sin nature will err. Thus, it natural that Mary would err.

[MarkBsnr]

we must insist that sinlessness and infallibility are two separate issues and do not have to coincide

I believe they do.

Sinlessness is without sin. Infallibility is never erring in any way. Let's assume for the sake of argument that a person is sinless. Yet that person can make an error. The person is still sinless.

Now let's assume that a person is infallible - they never make a mistake in understanding and believing what is required of God, yet they can still sin.

Those who have a sin nature will err. Thus, it natural that Mary would err.

It is natural that the offspring of Mary have a human father, too.