Books: The Last Puritan (1936)
Scepticism and Animal Faith (1923)
Realms of Being (1927-1940)
The Life of Reason
Character and Opinion in the U.S
Interpretations of Poetry and Religion

Santayana holds that one who really succeeds in doubting all that can be doubted will have no belief in his own existence, for a mind must exist over time and one has no guarantee that there is any reality than that of this moment. If "this moment" is the only reality we believe in, we are not taking it as a moment at all, but as something belonging to no time or place. So, for him, what is indubitable is typically an act of awareness of some kind of sensory pattern, an act of awareness which does not necessarily pertain to any continuing self.

"This scene", then, is an essence, that is, a definite pattern with its own individual character, but it is not an element in any real world, for a real world is one which things occur as phases through some sort of historical process. Thus this scene or essence, at least in the aspect of it the reality of which is guaranteed to us, is something which has a kind of being, but which does not exist in the ordinary sense.

For Santayana one returns from the sceptical stance with the recognition that the essences immediately given to consciousness have being but no existence. When we revert to our ordinary state we will come to believe that out acts of consciousness of these essences are in external relations, but will still see that the essences themselves cannot be, for each is complete in itself and not continuous with anything else. So, one will be instituting pure essences and will have no beliefs at all, and no factual knowledge.

"Animal faith": the acceptance in our minds of a whole stock of beliefs which are psychologically, ultimately biologically, imposed on us, without having any ultimate grounds for them.

View of the world:

(i) essence: a quality or form which might either come before a mind as its immediate object of attention or might pertain to a physical reality as its present character ("a quality swimming in consciousness").

(ii) matter: it comprises the whole flux of physical processes; constantly changing but abiding by certain fixed laws and habits.

(iii) spirit: it should be distinguished from "psyche": lower lying within the spirit to produce behaviour which will keep the organism as close as possible to some inherited ideal as presented case allows. The spirit is a physical process having an entirely physical explanation, ultimately probably by the laws of physica and chemistry; fruition of life; seat of all values.

(iv) truth: that by relation to which beliefs are either symbolically or literally true.

Santayana's pragmatism: most human belief is to be judged true or false according to its effects in adjusting us to and helping us make the best of the reality we are in the midst of and ourselves.

For Santayana, all action inspired by conscious choice is action for the sake of good. When we aim at something it presents itself to our consciousness as falling under the form of the good, that is, as possessing a quality of goodness. Goodness is an essence consisting in a kind of glow or sparkle which some things were for us.

However, they only wear that glow or sparkle for us because unconscious psychic forces are propelling us towards what seems to possess it, so that quite different states of affairs possess the quality of goodness as they present themselves to different people.

Reason: an organizing principle in the psyche, and urge to develop a steady and stable pattern of life, values and beliefs in which all our initial impulses are given as much of a head as is compatible with their being organized into a coherent unity.

The spiritual life is simply one human ideal, the satisfaction of which is given considerable, but not unlimited, weight in rational and social policies.