It’s not (ahem) easy reading. To add to the natural complexities of metaphysics, Blackham’s style seems to depend on writing as many sentences which include sometimes lengthy clauses which do not require commas to separate them as he can. Kierkegaard is easier to understand than Blackham’s précis of him – not true for the other five, though.
Blackham was a humanist, a bigwig in the Ethical Culture Society. I’m probably wrong, but I have a feeling that to know what the Ethical Culture Society is requires having hung out with Upper West Side New York Jewish intellectuals in the 1950’s. (I’m not going to include the Wikipedia links because I don’t want to lose your attention.)
Kierkegaard. Question: (a) Fear and Either? (b) Sickness and Or? (c) Death and Trembling? Answer: (d) Joker and Thief. (“There must be a way out of here,” said one to the other.)
Nietzsche: the first non-thinking philosopher; automatic philosophy (like automatic writing). From time to time Blackham is forced to note that he is referring to Nietzsche’s thought in his middle period, the implication being that the thought of his early and late periods were otherwise.
Gabriel Marcel. New name to me. The odd man out. Considering the Ethical Cultural Society’s sensitivity to the charge of atheism, perhaps he is the book’s token believing Christian (a Catholic, at that).
Jasper. I’d never read Jasper, since I knew he would be incomprehensible, or over my head, depending on how you look at it. From Blackham’s essay it would appear that Jasper’s contribution – and it was brilliant – was to bring human relations out of its ethics, morals, theology niches and treat it as a basic element of being.
Heidegger (whom I also have not read, for the same reason) found a word that is untranslatable into English, dasein, whose definition is Heidegger’s complete philosophical system, of which dasein is the defining principle.
Sartre: philosopher, poseur (not philosophe posé), ideologue. Nausea, plus one or two good essays or lectures on it, and classic existentialism becomes quite clear. In philosophy, that’s a great achievement. Nausea is not a fictionalization of a philosophical system. It’s the other way around. Being and Nothingness is a metaphysical monograph on the philosophy of Nausea.