Socrates 

Socrates was an ancient Greek philosopher, one of the three greatest figures of the ancient period of Western philosophy (the others were Plato and Aristotle), who lived in Athens in the 5th century BCE. … He was the first Greek philosopher to seriously explore questions of ethics.

    1. “The only true wisdom is in knowing you know nothing.”

    2. “The unexamined life is not worth living.”

    3. “I cannot teach anybody anything. I can only make them think”

    4. “Be kind, for everyone you meet is fighting a hard battle.”

    5. “Strong minds discuss ideas, average minds discuss events, weak minds discuss people.”

    6. “To find yourself, think for yourself.”

    7. “Education is the kindling of a flame, not the filling of a vessel.”

    8. “By all means marry; if you get a good wife, you’ll become happy; if you get a bad one, you’ll become a philosopher.” Lol this was funny!

    9. “He who is not contented with what he has, would not be contented with what he would like to have.”

    10. “Be slow to fall into friendship, but when you are in, continue firm and constant.”

    11. “If you don’t get what you want, you suffer; if you get what you don’t want, you suffer; even when you get exactly what you want, you still suffer because you can’t hold on to it forever. Your mind is your predicament. It wants to be free of change. Free of pain, free of the obligations of life and death. But change is law and no amount of pretending will alter that reality.”

    12. “Sometimes you put walls up not to keep people out, but to see who cares enough to break them down.”

    13. “The secret of happiness, you see, is not found in seeking more, but in developing the capacity to enjoy less.”

    14. “Death may be the greatest of all human blessings.”

    15. “Know thyself.” 

If you want to read more of his thought u can  just search for quotes of socrates, and you’ll get bunch of them. Which are so meaningful. He is one of the best philosopher.