Essence in the context of "Existence"

Rationality is the quality of being guided by or based on reason. In this regard, a person acts rationally if they have a good reason for what they do, or a belief is rational if it is based on strong evidence. This quality can apply to an ability, as in a rational animal, to a psychological process, like reasoning, to mental states, such as beliefs and intentions, or to persons who possess these other forms of rationality. A thing that lacks rationality is either arational, if it is outside the domain of rational evaluation, or irrational, if it belongs to this domain but does not fulfill its standards.

There are many discussions about the essential features shared by all forms, or accounts, of rationality. According to reason-responsiveness accounts, to be rational is to be responsive to reasons. For example, dark clouds are a reason for taking an umbrella, which is why it is rational for an agent to do so in response. An important rival to this approach are coherence-based accounts, which define rationality as internal coherence among the agent's mental states. Many rules of coherence have been suggested in this regard, for example, that one should not hold contradictory beliefs or that one should intend to do something if one believes that one should do it.

Human nature comprises the fundamental dispositions and characteristics—including ways of thinking, feeling, and acting—that humans are said to have naturally. The term is often used to denote the essence of humankind; however, this usage has proven to be controversial in that there is dispute as to whether or not such an essence actually exists.

Arguments about human nature have been a central focus of philosophy for centuries and the concept continues to provoke lively philosophical debate. While both concepts are distinct from one another, discussions regarding human nature are typically related to those regarding the comparative importance of genes and environment in human development (i.e., nature versus nurture). Accordingly, the concept also continues to play a role in academic fields, such as both the natural and the social sciences, and philosophy, in which various theorists claim to have yielded insight into human nature. Human nature is traditionally contrasted with human attributes that vary among societies, such as those associated with specific cultures.

The soul is the purported immaterial aspect or essence of a living being. It is typically believed to be immortal and to exist apart from the material world. The three main theories that describe the relationship between the soul and the body are interactionism, parallelism, and epiphenomenalism. Anthropologists and psychologists have found that most humans are naturally inclined to believe in the existence of the soul and that they have interculturally distinguished between souls and bodies.

The soul has been the central area of interest in philosophy since ancient times. Socrates envisioned the soul to possess a rational faculty, its practice being man's most godlike activity. Plato believed the soul to be the person's real self, an immaterial and immortal dweller of our lives that continues and thinks even after death. Aristotle sketched out the soul as the "first actuality" of a naturally organized body—form and matter arrangement allowing natural beings to aspire to full actualization.

Ousia (/ˈuːziə, ˈuːsiə, ˈuːʒə, ˈuːʃə/; Ancient Greek: οὐσία) is a philosophical and theological term, originally used in ancient Greek philosophy, then later in Christian theology. It was used by various ancient Greek philosophers, especially Aristotle, as a primary designation for philosophical concepts of essence or substance. It is analogous to concepts of being and the ontological in contemporary philosophy. In Christian theology, the concept of θεία ουσία (divine essence) is one of the most important doctrinal concepts, central to the development of trinitarian doctrine.

The Ancient Greek term θεία ουσία (theia ousia; divine essence) was translated in Latin as essentia or substantia, and hence in English as essence or substance.

Nature has two inter-related meanings in philosophy and natural philosophy. On the one hand, it means the set of all things which are natural, or subject to the normal working of the laws of nature. On the other hand, it means the essential properties and causes of individual things.

How to understand the meaning and significance of nature has been a consistent theme of discussion within the history of Western Civilization, in the philosophical fields of metaphysics and epistemology, as well as in theology and science. The study of natural things and the regular laws which seem to govern them, as opposed to discussion about what it means to be natural, is the area of natural science.