Read these lines: "Whence, I often asked myself, did the principle of life proceed? It was a bold question, and one which has ever been considered as a mystery. To examine the causes of life, we must first have recourse to death. I became acquainted with the science of anatomy, but this was not sufficient." What does the third sentence explain?

1. 1. The question he sets himself is where the principle of life comes from. 2. 2. The third sentence states his method: to examine life, one must first have recourse to death. 3. 3. The next sentence shows him acting on it by taking up anatomy. 4. 4. He does not abandon the question, and he says outright that anatomy was not sufficient. _Source: Frankenstein by Mary Shelley (1818)_