Explanation: Marcus Aurelius was a Roman Emperor who is noted for his philosophical musings, recorded in his personal notes, which were posthumously published as his Meditations. The title is a quote from the Meditations, emblematic of the philosophy of Stoicism that Aurelius espoused. To the Stoics, suffering came from within - by tormenting oneself over things one could not change, past, present, or future, one inflicted unhappiness upon oneself. The path to happiness, then, was to do what one could, and refuse to worry about what matters one could not change.

Stoicism and Cynicism were both related Greek philosophies of the period which stemmed from the same roots. While both philosophies held appeal to the Romans, Stoicism, which espoused reason and duty as the path to ataraxia (the state of non-suffering) and harmony, was generally more accepted in Roman culture than Cynicism. While Cynicism's "Go with your gut, overthinking will lead you astray" thinking was also appealing to the Romans, the broader rejection of social norms was generally disdained by Roman culture. What's next, acting like BARBARIANS!?

Cynicism, for that matter, comes from the Greek word for 'dog', after Diogenes of Sinope, a homeless philosopher who hung out with stray dogs and often compared himself to them, and influenced both Cynicism and Stoicism in seeking a natural, minimalistic order to life and happiness.

Both philosophies which espoused a view of the world as having an intrinsic harmony that could be discovered and adhered to for human happiness; thus, animals, while 'brutish', were often seen as themselves acting in accordance with this intrinsic harmony. A dog doesn't worry about philosophical matters, after all!

*Barkus