emphasis If you say that one thing is tantamount to a second, more serious thing, you are emphasizing how bad, unacceptable, or unfortunate the first thing is by comparing it to the second. What Bracey is saying is tantamount to heresy. be tantamount to sth if an action, suggestion, plan etc is tantamount to something bad, it has the same effect or is almost as bad (tantamount (1600-1700), from tant amunter )
being essentially equal to something; "it was as good as gold"; "a wish that was equivalent to a command"; "his statement was tantamount to an admission of guilt"