Post History
Ideas are not copyrightable. Having a character follow a philosophy is definitely not a form of plagiarism. Presenting that philosophy as a paraphrase of the original work might be plagiarism, thou...
Answer
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/23870 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
_Ideas_ are not copyrightable. Having a character follow a philosophy is definitely not a form of plagiarism. Presenting that philosophy as a paraphrase of the original work _might_ be plagiarism, though dubiously illegal (copyright on most of these works has long expired already anyway.) In most cases, if you just follow the idea but express it in your own way, this just falls under _drawing inspiration_ which is an entirely legal, common and perfectly acceptable practice. It's still a good form to credit the original author, possibly in an afterword, or similar "paraphernalia." There's definitely no need to add footnotes to the fictional story or follow academic practices of bibliography or such - you're neither violating copyright nor writing a paper that needs to follow academic scrutiny. But giving a credit where it's due is a _good savior-vivre_, not obligatory but welcome.