"I have never been able really to regret anything in all my life," says Mersault. "I've always been far too much absorbed in the present moment, or the immediate future, to think back." 
 Mersault is the very picture of hedonistic self-interest, enjoying the sensory pleasures of life while remaining completely impassive to the emotions of others. He approaches the world only as it bores or interests him, with a certain lack of imagination or curiosity about the inner lives of others. It seems to be a matter of shallow affect, rather than any actual malice... but it's jarring, all the same. 
 He lives aimlessly, floating on a stream of persistent nihilism, without driving ambitions or strong opinions of his own. The resultant wishy-washiness makes him a tool of his circumstances: he commits immoral acts on the suggestions of others without batting an eye, but just as easily might have been nudged into committing 'moral' ones, as long as he was asked in an amiable fashion. It seems to be 'the heat' and 'the sun' that drives him to violence - or so he claims. He seems emotionally blind to himself, as well as to others, only able to see his own emotional state as reflected elsewhere... or perhaps he's simply externalizing all blame by force of habit. 
 In his final outburst, Mersault neatly summarizes his nihilism: "What difference could they make to me, the deaths of others, or a mother's love, or his God; or the way a man decides to live, the fate he thinks he chooses... All alike would be condemned to die one day; his turn, too, would come like the others'." Discussion of religion in The Stranger is limited to Christianity, but somehow it reminded me of the parts of Buddhism that appeal to me the least: the idea of meditating on impermanence and on the concept of "no-self", both of which feel to me personally like they would lead me down a similar/unpleasant spiral of nihilism. 
 Somehow, at the end, Mersault ends his life happily (?), realizing his happiness-in-the-moment and the "benign indifference to the universe". It's like a kind of dark side to meditation, I suspect, devoid of trying to relieve the suffering of others, content to be mired in your own moment. 
 This is one of those books I wish I could discuss with other people, as I don't know much about existentialism or absurdism without the help of Wikipedia, and I'm sure I'm missing references / overtones / philosophical ideas.