At the root and trunk of the diagram of the tree one finds the 'immune responses, basic reflexes and metabolic regulation'. The section above, where the first distinctions are made, reveals 'pain and pleasure behaviour'. Then we reach 'drives and motivations', and when the branches really become diversified we have reached 'emotions'. The top section with many small branches represents the area of 'feelings'. On each of these levels a person will steer away from pain and try to maintain the homeostasis that is beneficial for well-being and survival. Damasio asserts that 'feelings' play an important role in social behaviour and shows this by telling stories about patients, and he explains how the (lack of) capacity for certain social feelings can be neurologically understood from certain conditions of a brain which can be literally shown on a brain-map. Social feelings, like embarrassment, shame, guilt, contempt, indignation, sympathy, compassion, awe, wonder, elevation, gratitude and pride, are also rooted in all other levels where homeostatic regulation takes place. Damasio proposes a definition of what a feeling is: "a feeling is a perception of a certain state of the body along with the perception of a certain mode of thinking and of thoughts with certain themes." (Damasio 2004, 86).
Damasio came to this conclusion by working for many years with people who have brain injuries and by researching the brain as a neurological scientist. In his latest book Damasio connects his findings from his practice in neurology to the work of Spinoza, the philosopher who lived three and a half centuries earlier in Amsterdam. There is a crucial quote from Spinoza, which Damasio has cherished throughout his life and which inspired him to write this book. After 30 years of neurological research Damasio finds that the observations that Spinoza made in the 17th century resonate deeply with his findings in neurology.
Virtutis fundamentum esse ip sum conatum proprium esse conservandi, et felicitatem in eo consistere, quod homo suum esse conservare potest." (Proposition 18, part IV, Ethics, Spinoza).
Damasio paraphrases this quote in 'deeply American terms' as follows: "I hold these truths to be self-evident, that all human beings are created such that they tend to preserve their life and seek well-being, that their happiness comes from the successful endeavour to do so, and that the foundation of virtue rests on these facts." (Damasio 2004, 171). Spinoza and Damasio both understand that "the biological reality of self-preservation leads to virtue because in our inalienable need to maintain ourselves we must, of necessity, help preserve other selves." (Damasio 2004, 171). Damasio suggests that this insight "contains the foundation for a system of ethical behaviours and that foundation is neurobiological. The foundation is the result of a discovery based on the observation of human nature rather than the revelation of a prophet." (Damasio 2004, 171).
For 'the thinking actor' this insight involves a careful monitoring of feelings to be able to recognise in what direction well-being and survival can be found. This may be simple to see in a baby. When people get older it often becomes more complex and/or more difficult to consciously perceive when feelings of happiness or feelings of sadness arise. As actors, people have to perform and persevere, earn a living and deal with the situations of life. The brain constantly informs a human being with signals about emotions, but how these are interpreted is a different issue. The constant flux of input about emotions colours the perceptions of the situation an actor is in. Damasio argues that during childhood one of the purposes of education and development is to teach a human being to adapt to a certain culture by learning how to interpret and evaluate this flux of emotions. From this perspective one could even argue, as Damasio proposes, "that social conventions and ethical rules may be seen in part as extensions of the basic homeostatic arrangements at the level of society and culture." (Damasio 2004,168).