Fundamental truths and core principles of investing don't change. Only their application evolves with time, say famed value investor Warren Buffett and his mentor Benjamin Graham.
A first principle is a proposition that forms the foundation for a body of knowledge. First principles cannot be deduced from other propositions or assumptions.
"As to methods, there may be a million and then some, but principles are few. The man who grasps principles can successfully select his own methods. The man who tries methods, ignoring principles, is sure to have trouble."
Benjamin Graham — the founder of Value Investing — taught that the foundation of successful investing was the Margin of Safety.
Graham also wrote:
"The underlying principles of sound investment should not alter from decade to decade, but the application of these principles must be adapted to significant changes in the financial mechanisms and climate."
Graham's most famous pupil — Warren Buffett — has reiterated on multiple occasions that the principles of sound investing have not changed one iota since his mentor defined them nearly a century ago.