1. â€œThe unexamined life is not worth livingâ€ â€“ Socrates (470-399 BCE)
Socratesâ€™ belief that we must reflect upon the life we live was partly inspired by the famous phrase inscribed at the shrine of the oracle at Delphi, â€œKnow thyself.â€ The key to finding value in the prophecies of the oracle was self-knowledge, not a decoder ring.
Socrates felt so passionately about the value of self-examination that he closely examined not only his own beliefs and values but those of others as well. More precisely, through his relentless questioning, he forced people to examine their own beliefs. He saw the citizens of his beloved Athens sleepwalking through life, living only for money, power, and fame, so he became famous trying to help them.
2. â€œEntities should not be multiplied unnecessarilyâ€ â€“ William of Ockham (1285 – 1349?)
Commonly known as Ockhamâ€™s razor, the idea here is that in judging among competing philosophical or scientific theories, all other things being equal, we should prefer the simplest theory. Scientists currently speak of four forces in the universe: gravity, the electromagnetic force, the strong nuclear force, and the weak nuclear force. Ockham would certainly nod approvingly at the ongoing attempt to formulate a grand unified theory, a single force that encompasses all four.
The ultimate irony of Ockhamâ€™s razor may be that some have used it to prove God is unnecessary to the explanation of the universe, an idea Ockham the Franciscan priest would reject.
3. â€œThe life of man [is] solitary, poor, nasty, brutish, and short.â€ â€“ Thomas Hobbes (1588 â€“ 1679)
Referring to the original state of nature, a hypothetical past before civilization, Hobbes saw no reason to be nostalgic.
Whereas Rousseau said, â€œMan is born free, and he is everywhere in chains,â€ Hobbes believed we find ourselves living a savage, impossible life without education and the protection of the state. Human nature is bad: weâ€™ll prey on one another in the most vicious ways. No doubt the state imposes on our liberty in an overwhelming way. Yet Hobbesâ€™ claim was that these very chains were absolutely crucial in protecting us from one another.
4. â€œI think therefore I amâ€ â€“ RenÃ© Descartes (1596 â€“ 1650)
Descartes began his philosophy by doubting everything in order to figure out what he could know with absolute certainty. Although he could be wrong about what he was thinking, that he was thinking was undeniable. Upon the recognition that â€œI think,â€ Descartes concluded that â€œI am.â€
On the heels of believing in himself, Descartes asked, What am I? His answer: a thinking thing (res cogitans) as opposed to a physical thing extended in three-dimensional space (res extensa). So, based on this line, Descartes knew he existed, though he wasnâ€™t sure if he had a body. Itâ€™s a philosophical cliff-hanger; youâ€™ll have to read Meditations to find out how it ends.
5. â€œTo be is to be perceived (Esse est percipi).â€ Or, â€œIf a tree falls in the forest and no one is there to hear it, does it make a sound?â€ â€“ Bishop George Berkeley (1685 â€“ 1753)
As an idealist, Berkeley believed that nothing is real but minds and their ideas. Ideas do not exist independently of minds. Through a complicated and flawed line of reasoning he concluded that â€œto be is to be perceived.â€ Something exists only if someone has the idea of it.
Though he never put the question in the exact words of the famous quotation, Berkeley would say that if a tree fell in the forest and there was no one (not even a squirrel) there to hear it, not only would it not make a sound, but there would be no tree.
The good news is, according to Berkeley, that the mind of God always perceives everything. So the tree will always make a sound, and thereâ€™s no need to worry about blipping out of existence if you fall asleep in a room by yourself.
6. â€œWe live in the best of all possible worlds.â€ â€“ Gottfried Wilhelm Leibniz (1646 â€“ 1716)
Voltaireâ€™s famous novel Candide satirizes this optimistic view. And looking around you right now you may wonder how anyone could actually believe it. But Leibniz believed that before creation God contemplated every possible way the universe could be and chose to create the one in which we live because itâ€™s the best.
The principle of sufficient reason holds that for everything, there must be sufficient reason why it exists. And according to Leibniz the only sufficient reason for the world we live in is that God created it as the best possible universe. God could have created a universe in which no one ever did wrong, in which there was no human evil, but that would require humans to be deprived of the gift of free wills and thus would not be the best possible world.
7. â€œThe owl of Minerva spreads its wings only with the falling of the dusk.â€ G.W.F. Hegel (1770 â€“ 1831)
Similar to â€œvision is 20/20 in hindsight,â€ Hegelâ€™s poetic insight says that philosophers are impotent. Only after the end of an age can philosophers realize what it was about. And by then itâ€™s too late to change things. It wasnâ€™t until the time of Immanuel Kant (1724 – 1804) that the true nature of the Enlightenment was understood, and Kant did nothing to change the Enlightenment; he just consciously perpetuated it.
Marx (1818 â€“ 1883) found Hegelâ€™s apt description to be indicative of the problem with philosophy and responded, â€œthe philosophers have only interpreted the world differently, what matters is to change it.â€
8. â€œWho is also aware of the tremendous risk involved in faith â€“ when he nevertheless makes the leap of faith â€“ this [is] subjectivity â€¦ at its height.â€ â€“ SÃ¸ren Kierkegaard (1813 â€“ 1855)
In a memorable scene from Indiana Jones and the Last Crusade, Indy deduced that the final step across his treacherous path was a leap of faith. And so it is in Kierkegaardâ€™s theory of stages of life.The final stage, the religious stage, requires passionate, subjective belief rather than objective proof, in the paradoxical and the absurd. So, whatâ€™s the absurd? That which Christianity asks us to accept as true, that God became man born of a virgin, suffered, died and was resurrected.
Abraham was the ultimate â€œknight of faithâ€ according to Kierkegaard. Without doubt there is no faith, and so in a state of â€œfear and tremblingâ€ Abraham was willing to break the universal moral law against murder by agreeing to kill his own son, Isaac. God rewarded Abrahamâ€™s faith by providing a ram in place of Isaac for the sacrifice. Faith has its rewards, but it isnâ€™t rational. Itâ€™s beyond reason. As Blaise Pascal said, â€œThe heart has its reason which reason does not know.â€
9. â€œGod is dead.â€ â€“ Friedrich Nietzsche (1844 â€“ 1900)
Well, you might not hear this one in a graduation speech, but youâ€™ll probably hear it in college. Actually, Nietzsche never issued this famous proclamation in his own voice but rather put the words in the mouth of a character he called the madman and later in the mouth of another character, Zarathustra.
Nevertheless, Nietzsche endorsed the words. â€œGod is deadâ€ is often mistaken as a statement of atheism. It is not, though Nietzsche himself was an atheist. â€œDeadâ€ is metaphorical in this context, meaning belief in the God of Christianity is worn out, past its prime, and on the decline. God is lost as the center of life and the source of values. Nietzscheâ€™s madman noted that himself came too soon. No doubt Nietzsche, too, thought he was ahead of his time in heralding this news.
10. â€œThere is but one truly serious philosophical problem, and that is suicide.â€ â€“ Albert Camus (1913 â€“ 1960)
Camusâ€™ solution to the philosophical problem was to recognize and embrace lifeâ€™s absurdity. Suicide, though, remains an option if the absurdity becomes too much. Indeed Camusâ€™ own death in a car crash was ambiguous. Was it an accident or suicide?
For Camus, the absurd hero is Sisyphus, a man from Greek mythology who is condemned by the gods for eternity to roll up a stone up a hill only to have it fall back again as it reaches the top. For Camus, Sisyphus typified all human beings: we must find a meaning in a world that is unresponsive or even hostile to us. Sisyphus, Camus believed, affirms life, choosing to go back down the hill and push the rock again each time. Camus wrote: â€œThe struggle itself toward the heights is enough to fill a manâ€™s
heart. One must imagine Sisyphus happy.â€
11. â€œOne cannot step twice in the same river.â€ â€“ Heraclitus (ca. 540 â€“ ca. 480 BCE)
Heraclitus definitely isnâ€™t alone here. His message was that reality is constantly changing itâ€™s an ongoing process rather than a fixed and stable product. Buddhism shares a similar metaphysical view with the idea of annica, the claim that all reality is fleeting and impermanent.
In modern times Henri Bergson (1859 â€“ 1941) described time as a process that is experienced. An hour waiting in line is different from an hour at play. Today contemporary physics lends credence to process philosophy with the realization that even apparently stable objects, like marble statues, are actually buzzing bunches of electrons and other subatomic particles deep down.