Leonardo da Vinci on thinking

Iron rusts from disuse; stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigor of the mind.

Simplicity is the ultimate sophistication.

Anyone who invokes authors in discussion is not using his intelligence but his memory.

Great minds discuss ideas. Average minds discuss events. Small minds discuss people.

Eleanor Roosevelt1884–1962

• Ideas

It is the mark of an educated mind to be able to entertain a thought without accepting it.

Aristotle384–322 BC

• Education
• Ideas

He who learns but does not think, is lost! He who thinks but does not learn is in great danger.

Confucius551–479 BC

• Education