Aristotle (384–322 BC)
“λόγον δὲ μόνον ἄνθρωπος ἔχει τῶν ζῴων”
(“Man alone of all animals possesses speech”)
    Aristotle regarded rationality as the crucial differentiating characteristic of human beings. Scientific understanding was glorious.
    Aristotle was a ginormous advocate for reasoning! Not only did he invent the subject of logic, his analysis is still taught today. Amazingly, no one made a significant addition to the subject until Gottlob Frege in the late 1800's! Then Frege touched off a revolution in the science of logic!
    Aristotle was Alexander the Great's tutor; and according to an Islamic tradition, Aristotle lectured Alexander on the importance of alcoholic sobriety. Aristotle always advocated rational self-control. He was especially ga-ga for the virtue called ‘temperance’ (meaning ‘moderation’) as guided by the concept of ‘the Golden Mean of virtue’:

    “If therefore the way in which every art or science performs its work well is by looking to the mean and applying that as a standard to its productions (hence the common remark about a perfect work of art, that you could not take from it nor add to it—meaning that excess and deficiency destroy perfection, while adherence to the mean preserves it)—if then, as we say, good craftsmen look to the mean as they work, and if virtue, like nature, is more accurate and better than any form of art, it will follow that virtue has the quality of hitting the mean.
    “I refer to moral virtue, for this is concerned with emotions and actions, in which one can have excess or deficiency or a due mean. For example, one can be frightened or bold, feel desire or anger or pity, and experience pleasure and pain in general, either too much or too little, and in both cases wrongly; whereas to feel these feelings at the right time, on the right occasion, towards the right people, for the right purpose and in the right manner, is to feel the best amount of them, which is the mean amount—and the best amount is of course the mark of virtue. And similarly there can be excess, deficiency, and the due mean in actions. Now feelings and actions are the objects with which virtue is concerned; and in feelings and actions excess and deficiency are errors, while the mean amount is praised, and constitutes success; and to be praised and to be successful are both marks of virtue. Virtue, therefore is a mean state in the sense that it is able to hit the mean. Again, error is multiform (for evil is a form of the unlimited,...and good of the limited), whereas success is possible in one way only (which is why it is easy to fail and difficult to succeed—easy to miss the target and difficult to hit it); so this is another reason why excess and deficiency are a mark of vice, and observance of the mean a mark of virtue.”

“Excellence is never an accident. It is always the result of high intention, sincere effort, and intelligent execution; it represents the wise choice of many alternatives – choice, not chance, determines your destiny.”

“Learning is not child's play; we cannot learn without pain.”

“It is well to be up before daybreak, for such habits contribute to health, wealth, and wisdom.”

“I count him braver who overcomes his desires than him who conquers his enemies; for the hardest victory is over self.”

“Happiness depends upon ourselves.”

“Through discipline comes freedom.”

“The happy life is regarded as a life in conformity with virtue.”

“The beauty of the soul shines out when a man bears with composure one heavy mischance after another, not because he does not feel them, but because he is a man of high and heroic temper.”

“He who has overcome his fears will truly be free.”

“Courage is the first of human qualities because it is the quality which guarantees the others.”
[Because it takes courage to face difficult facts and because:
“To love truth for truth's sake is the principal part of human perfection in this world, and the seed-plot of all other virtues.”
    John Locke]

“The least initial deviation from the truth is multiplied later a thousand fold.”

“For though we love both the truth and our friends, piety requires us to honor the truth first.”

“Misfortune shows those who are not really friends.”

“Liars when they speak the truth are not believed.”

“Where your talents and the needs of the world cross, there lies your vocation.”

“The only stable state is the one in which all men are equal before the law.”

“Equality consists in the same treatment of similar persons.”

“For what is the best choice, for each individual is the highest it is possible for him to achieve.”

“Man is a goal seeking animal. His life only has meaning if he is reaching out and striving for his goals.”

“Poverty is the parent of revolution and crime.”

“The most perfect political community is one in which the middle class is in control, and outnumbers both of the other classes.”

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

“Teenagers these days are out of control. They eat like pigs, they are disrespectful of adults, they interrupt and contradict their parents, and they terrorize their teachers.”

“The gods too are fond of a joke.”

“The secret to humor is surprise.”

“The greatest thing by far is to be a master of metaphor; it is the one thing that cannot be learned from others; and it is also a sign of genius, since a good metaphor implies an intuitive perception of the similarity of the dissimilar.”

“The aim of art is to represent not the outward appearance of things, but their inward significance.”

“The one exclusive sign of thorough knowledge is the power of teaching...The proof that you know something is that you are able to teach it.”

“Knowing yourself is the beginning of all wisdom.”

“The society that loses its grip on the past is in danger, for it produces men who know nothing but the present, and who are not aware that life had been, and could be, different from what it is.”

“Wicked men obey from fear; good men, from love.”

“We are what we repeatedly do. Excellence, then, is not an act, but a habit.”

“Good habits formed at youth make all the difference.”

“The educated differ from the uneducated as much as the living from the dead.”

“Friends hold a mirror up to each other; through that mirror they can see each other in ways that would not otherwise be accessible to them, and it is this mirroring that helps them improve themselves as persons.”

“Men create gods after their own image, not only with regard to their form but with regard to their mode of life.”