It's a delightful read in the philosophical realm of understanding what really humanity is. Here Mark Twain tries to present some of his convictions regarding mankind. The book is in the form of conversation between two individuals who are young and old man respectively.

Mark Twain believes that what he is professing is not a philosophy but indeed a fact. One of the central themes of the book can be seen in this paragraph-
"Man the machine—man the impersonal engine. Whatsoever a man is, is due to his MAKE, and to the INFLUENCES brought to bear upon it by his heredities, his habitat, his associations. He is moved, directed, COMMANDED, by EXTERIOR influences—SOLELY. He ORIGINATES nothing, not even a thought."

Another thing highlighted in the book is that every act done by man is to satisfy or content his own spirit and to win it's own approval. A lot of time is spent in explaining how every act is catered towards securing own peace of mind and every other consideration is secondary and indeed catered towards fulfilling the first goal. Mark Twain suggests this very approval or the principle can be termed as conscience.

In the later parts it was great to see how Mark Twain suggests that the intellectual stature of man and other beasts is mostly the same. He alludes this in this line-
" Man has a finer and more capable machine in him than those others, but it is the same machine and works in the same way."

As a whole the ideas are open to discussion and deliberation but it was surely an interesting read.