Is error in doctrine always sin?

[Fiyahstarter]

Originally Posted by Timmy

BTW, some doctrines are called a "doctrine of devils" or some such. Is it a sin to believe those doctrines? E.g., Trinitarianism has been called that here on AFF, if I recall. Any other examples? How about cessationism? Reincarnation? Deism?

And don't forget Timmyism.