Aristotle proposed the most prominent and sophisticated version of virtue ethics in Antiquity and his teachings have become authoritative for many scholars and still remain alive in the vital contributions of neo-Aristotelians in contemporary philosophy. His main ethical work is the Nicomachean Ethics ; less prominent but still valuable and authentic is the Eudemian Ethics while Aristotle’s authorship of the Magna Moralia is highly questionable. Aristotle claims that happiness (eudaimonia) is the highest good – that is the final, perfect, and self-contained goal – to which all people strive at. In particular, happiness is the goal of life, that is, a life that is devoted to “doing” philosophy (EN X, 6–9). Whether a person can be called “happy” can only be determined at the very end of a person’s life, retrospectively. For a good and general overview on Aristotle’s ethics see Broadie (1991) and Wolf (2007).
Over a long period of time, the slightly denser regions of the nearly uniformly distributed matter gravitationally attracted nearby matter and thus grew even denser, forming gas clouds, stars, galaxies, and the other astronomical structures observable today.  The details of this process depend on the amount and type of matter in the universe. The four possible types of matter are known as cold dark matter , warm dark matter , hot dark matter , and baryonic matter . The best measurements available, from Wilkinson Microwave Anisotropy Probe (WMAP), show that the data is well-fit by a Lambda-CDM model in which dark matter is assumed to be cold (warm dark matter is ruled out by early reionization ),  and is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about %.  In an "extended model" which includes hot dark matter in the form of neutrinos , then if the "physical baryon density" Ω b h 2 is estimated at about (this is different from the 'baryon density' Ω b expressed as a fraction of the total matter/energy density, which as noted above is about ), and the corresponding cold dark matter density Ω c h 2 is about , the corresponding neutrino density Ω v h 2 is estimated to be less than .