The science of ethics

About the book "It is beneficial for humans, before everything, to establish social relations among themselves, and to adhere to what would make them be one whole, and what contributes to strengthening the bond of friendship between them." A philosophical letter written by Spinoza and published by his friends after his death in 1677. The main message of this book is that everything is part of nature. The book is considered one of the most influential and discussed books in philosophy. It seems from the title that it talks about ethics as a branch of philosophy, but the book does not address this known meaning of the word "ethics" until the last part.