The philosophy of happiness is the philosophical concern with the existence, nature, and attainment of happiness. Some philosophers believe happiness can be understood as the moral goal of life or as an aspect of chance; indeed, in most European languages the term happiness is synonymous with luck. Thus, philosophers usually explicate on happiness as either a state of mind, or a life that goes well for the person leading it. Given the pragmatic concern for the attainment of happiness, research in psychology has guided many modern day philosophers in developing their theories. Democritus (c. 460 – c. 370 BC) is known as the 'laughing philosopher' because of his emphasis on the value of 'cheerfulness'. right Plato (c. 428 - c. 347 BCE) teaches in the Republic that a life committed to knowledge and virtue will result in happiness and self-realization. To achieve happiness, one should become immune to changes in the material world and strive to gain the knowledge of the eternal, immutable forms that reside in the realm of ideas. The Chariot Allegory from the Phaedrus is possibly Plato’s most important teaching on how to achieve inner happiness. Plato sees societal happiness stemming from citizens treating each other justly, leading virtuous lives, and each fulfilling their social function. Aristotle (384 – 322 BCE) was considered an ancient Greek scholar in the disciplines of ethics, metaphysics, biology and botany, amongst others. Aristotle described eudaimonia (Greek: εὐδαιμονία) as the goal of human thought and action. Eudaimonia is often translated to mean happiness, but some scholars contend that "human flourishing" may be a more accurate translation. More specifically, eudaimonia (arete, Greek: ἀρετή) refers to an inherently positive and divine state of being in which humanity can actively strive for and achieve. Given that this state is the most positive state for a human to be in, it is often simplified to mean happiness. However, Aristotle's use of the term in Nicomachiean Ethics extends beyond the general sense of happiness.