Twitter is a useful medium for the exchange of ideas, but it is not well suited to a thorough exposition of complex topics. In one recent exchange, I engaged author and journalist Peter Hitchens (@clarkemicah) on the relative harms of alcohol and cannabis, a discussion he later dissected in his blog (http://dailym.ai/13Dc1Rv). Having repeatedly attempted without success to post a reply on his blog, I have elected to do so here.