Euthymia (Greek: εὐθυμία, "gladness, good mood, serenity"—literally "good thumos") is a central concept in the moral thoughts of Democritus, who presents it as an ideal disposition of mind corresponding to a form of equanimity, a calm affectivity and relative steadiness of the soul.
Diogenes Laërtius records Democritus' view as follows: "The chief good he asserts to be cheerfulness (euthymia); which, however, he does not consider the same as pleasure; as some people, who have misunderstood him, have fancied that he meant; but he understands by cheerfulness, a condition according to which the soul lives calmly and steadily, being disturbed by no fear, or superstition, or other passion."[1]
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