Let there be but two occasions for speech - when the subject is one which you thoroughly know and when it is one on which you are compelled to speak. On these occasions alone is speech better than silence; on all others, it is better to be silent than to speak.
IsocratesThose who directed the state in the time of Solon and Cleisthenes did not establish a polity which ... trained the citizens in such fashion that they looked upon insolence as democracy, lawlessness as liberty, impudence of speech as equality, and licence to do what they pleased as happiness, but rather a polity which detested and punished such men and by so doing made all the citizens better and wiser.
IsocratesIt is more important to know where you are going than to get there quickly. Do not mistake activity for achievement. Remember that there is nothing stable in human affairs, therefore avoid undue elation in prosperity or undue depression in adversity.
IsocratesSo far has Athens left the rest of mankind behind in thought and expression that her pupils have become the teachers of the world, and she has made the name of Hellas distinctive no longer of race but of intellect, and the title of Hellene a badge of education rather than of common descent.
Isocrates