Re “invincible ignorance,” this entry from the <A

href=”http://www.newadvent.org/cathen/07648a.htm”>Catholic

Encyclopedia:

So far as fixing human responsibility, the most important division of ignorance is that designated by the terms invincible and vincible. Ignorance is said to be invincible when a person is unable to rid himself of it notwithstanding the employment of moral diligence, that is, such as under the circumstances is, morally speaking, possible and obligatory. This manifestly includes the states of inadvertence, forgetfulness, etc. Such ignorance is obviously involuntary and therefore not imputable. On the other hand, ignorance is termed vincible if it can be dispelled by the use of “moral diligence.”