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To lack knowledge has been thought to be due to being ignorant. And this is correct, because if you choose to ignore whatever knowledge is around, you then shall lack in that knowledge.
The saying that he or she is ignorant, is said in such a way as to purely demean, and to suggest that you are in some way beneath par as a human being, whilst in fact suggesting something else, and being correct in direct interpretation. Interpretation can be direct, or it can be altered in order to make whatever to look like something else.
© R. G. Crosbie