It is well known that, just as God has communicated many truths to man, so has Satan endeavoured to bring in many errors, his hope being to prejudice and weaken the reception of the truth even though he failed to induce men to entertain his lies. Indeed he finds that his best time for selling his wares is when pedlars are most busy, and when, in the busy market, men are buying truth. It is then that he offers his merchandise.
To make it more vendible he represents it as highly respectable and as spiritual in character as truth itself. For long he has walked as a prince of darkness, but because he has lost hope of deceiving men any longer as such, he now transforms himself as an angel of light. Successful in past ages as a bare-faced deceiver, he put on a mask when men discovered his real character, and thus disguised he carried on his designs for generations. But the mask is now taken off, and he operates as one wearing the very face of truth.Samuel Bolton, The True Bounds of Christian Freedom, p. 13
1. What Bolton took for granted, that Satan stands behind destructive theological error as its prime instigator, is largely a lost perspective today. It would prfoundly change the that Christians thought of encounters with the demonic if they connected them with heresies and false teaching. The NT evidence is not lacking in this regard.
2. The devil of course appeared from the beginning as an angel of light as he offered
an alternative revelation to Adam and Eve. He is most dangerous when he appears most benign, and his theological lies are sold to us as even better than truth itself.