no no no, he was not a mad, or crazy- why do people always seem interpret this incorrectly. he was more sane than the society he came from. he was genius, who had been hurt by the death of his family, killed by elitist war profiteers- exactly as things are today!. furthermore- the name nemo- is "omen" backwards...
Verne would have had knowledge of such craft. not that they existed but that the technology would soon be real. (the first true sub was not long invented after this book).
also- Nemo escaped tyranny, and the control of man.which is going on even more today.
he was genius and had found a way out. but knowledge - as is the point of this story (technology) is a double edged sword that we are to be aware of.
I state; Mans technology has now surpassed his ability to use it responsibly.
" Think of it: On the surface, there is hunger and fear. Men still exercise unjust laws. They fight and tear one another to pieces. A mere few feet beneath the waves, their reign ceases, their evil drowns. Here on the ocean floor is the only independence. Here, I am free. Imagine what would happen if they controlled machines such as this submarine boat. Far better that they think there's a monster and hunt me with harpoons..."
"There is hope for the future. When the world is ready for a new and better life, all this will someday come to pass... in God's good time."
this last line would apply even today. since the society has degenerated- or is in retrograde.