There were two key pieces of information that enabled Allen to quit later that day. First, the hypnotherapist told him smoking was "just nicotine addiction", which Allen had never perceived before that moment, i.e. that he was an addict. Second, his son John lent him a medical handbook which explained that the physical withdrawal from nicotine is just like an "empty, insecure feeling".[3] He claims that these two realisations crystallised in his mind just how easy it was to stop and so then enabled him to follow an overwhelming desire to explain his method to as many smokers as possible.[4]