Id, ego and superego in the context of "Beyond the Pleasure Principle"

The libido (/lɪˈbiːdoʊ/ lih-BEE-doh; from Latin libīdō) refers to a psychological energy that, in common parlance, encompasses all forms of sexual desire, but is sometimes also regarded as the driving force behind other needs, such as a mother's love for her infant. The term was originally developed by Sigmund Freud, the pioneer of psychoanalysis. Initially it referred only to specific sexual needs, but he later expanded the concept to a universal desire, with the id being its "great reservoir". As driving energy behind all life processes, libido became the source of the social engagement (maternal love instinct, for example), sexual behaviour, pursuit for nutrition, skin pleasure, knowledge and victory in all areas of self- and species preservation.

Equating the libido with the Eros of Platonic philosophy, Freud further differentiated two inherent operators: the life drive and the death drive. Both aspects are working complementary to each other: While the death drive, also called Destrudo or Thanatos, embodies the principle of 'analytical' decomposition of complex phenomenon, the effect of life drive (Greek Bios) is to reassemble or synthesise the parts of the decomposition in a way that serves the organisms regeneration and reproduction. Freud's most abstract description of libido represents an energetic potential that begins like a bow to tense up unpleasantly (noticeable 'hunger') in order to pleasantly relax again (noticeable satisfaction); its nature is both physical and psychological. Starting from the id in the fertilised egg, libido initiates also the emergence of two further instances: the ego (function of conscious perception), and the superego, which specialises in retrievable storage of experiences (long-term memory). Together with libido as their source, these three instances represent the common core of all branches of psychoanalysis.

Eros (/ˈɪərɒs/, US: /ˈɛrɒs, irɒs, -oʊs/; from Ancient Greek ἔρως (érōs) 'love, desire') is a concept in ancient Greek philosophy referring to sensual or passionate love, from which the term erotic is derived. Eros has also been used in philosophy and psychology in a much wider sense, almost as an equivalent to "life energy". Psychoanalysis uses the term to describe the universal desire that drives all innate needs (of the id), which according to Freud is identical to Plato's conception. The Protestant philosopher C. S. Lewis posits it as one of the four ancient Greek words for love in Christianity, alongside storge, philia, and agape.