Eudaimonia, happiness, and well-being
The standard definition of eudaimonia used to be that it denotes happiness. In recent decades a more satisfactory rendering has been found in notions such as those of well-being and human flourishing. These are far better than the older, 'happiness'. 'Happiness' suggests a merely pleasant and enjoyable state or condition to be. Eudaimonia is more metaphysical than this. To be eudaimon is a matter of being in the objectively correct state of living and acting well. This sense is common to both Plato and Aristotle.
In their more detailed analyses of the preconditions and components of eudaimonia, Plato and Aristotle diverge. Since there is not enough space to deal with their divergences, I fix on Aristotle on whom most current scholarship on eudaimonia - that particular concept in their ethical theories - focuses.
I don't think that term has 'has semi-mystical connotations (e.g. the daimon of Socrates)'. Etymologically it may have such associations but these make no significant appearance in Plato and Aristotle's ethical theories.
Analysis of eudaimonia
Anthony Price provides a dense but accurate and informative first approach to the fuller conceptualisation of eudaimonia:
'Let us state', Aristotle proposes, 'what is the highest of all goods
achievable by action' ([Nicomachean Ethics] I 4, 1095aI4 ff.). 'Verbally', he suggests,
'there is very general agreement; for both the general run of men
and people of superior refinement say that it is eudaimonia, and
identify living well and doing well with being eudaimon, but with
regard to what eudaimonia is they differ, and the many do not give
the same account as the wise. For the former think it is some plain
and obvious thing, like pleasure, wealth, or honour' (Io95aI7 if.,
with, here as elsewhere, Aristotle's eudaimonia and eudaimon for [Sir David]
Ross's 'happiness' and 'happy'). Here are two quite different
questions about eudaimonia, contrasted not by any form of words,
but by the fact that the many and the wise give the same answer
to the one question, different answers to the other: they agree that
eudaimonia is 'living well and doing well', but not whether 'it is
some plain and obvious thing, like pleasure, wealth, or honour'.
After J. L. Austin, we may say that they agree on a rough analysis
of eudaimonia (living and doing well), but not on its specification
(what fills the bill of living and doing well).
Now if Aristotle is right, the many and the wise agree not only
about what, minimally and analytically, eudaimonia is, but also
that it is 'the highest of all goods achievable by action' (I 4,
1095aI6 f.). He implies that there are other, lower, practical
goods. But this is ambiguous. It may amount to the all-good-within
thesis: all practical goods are good solely for the sake of eudaimonia.
Or it may assume the some-good-without thesis-some practical
goods are good not at all, or not solely, for the sake of eudaimonia
- with, at most, the proviso that any practical goodness for the sake
of eudaimonia outweighs any practical goodness not for its sake.
(A far weaker proviso would be that the goodness of eudaimonia
as a whole outweighs any independent practical goodness.) On
the some-good-without thesis, eudaimonia may be paramount
among practical goods, perhaps even to the extent that 'for the
sake of eudaimonia' always has priority as a reason for action. On
the all-good-within thesis, eudaimonia is fundamental among
practical goods, in the sense that 'for the sake of eudaimonia' has,
in the last resort, a monopoly as a reason for action. Note further
that Aristotle could try to make out the all-good-within view in
two ways: by restricting practical goods, or by extending
eudaimonia to cover a multiplicity of practical goods. So the all-
good-within view has itself an exclusive, and an inclusive, variant
(of which the second is more likely to be plausible). On any view,
I take it, Aristotle is defining, not prescribing. To adopt a specific
conception of eudaimonia is to accept of certain reasons for action
that they override or underpin other reasons. (A.W. Price, 'Aristotle's Ethical Holism', Mind, Vol. 89, No. 355 (Jul., 1980), pp. 338-352: 338-9.)
Eudaimonia, emotions and the intellect
At a lower level of abstraction, Aristotle distinguishes two components of eudaimonia, or two areas of its operation in our lives : the emotions and the intellect.
The emotions of a person possessing eudaimonia are intermediate between excess and defect. In action such a person exhibits neither foolhardiness (thrasos) nor cowardice (deilia) but courage (andreia) where courage is the ability to pursue one's objectives with due regard for danger and hazard and equal disregard for shrink-back, disabling fear. Courage is a 'mean' or intermediate state between excess (huperbole) and deficiency (elleipsis).
Aristotle enumerates and specifies a number of such intermediates in NE, II.7 & III.
There is more to eudaimonia than observing the mean between emotions when we act, even when this is a mater of habit instilled by moral education. We are cognitive as well as practical beings. To have eudaimonia we also need to develop our minds to encompass intellectual excellences. Aristotle spells these out in NE.VI : art or practical skill (techne), science or systematic knowledge (episteme), prudence or practical wisdom (phronesis), wisdom or (roughly) knowledge of the first principles of reality (sophia), and intuitive reason (nous).
If the above is right, or even approximately correct, you will see I think that eudaimonia has no connexion with the semi-mystical or the holy spirit. Its feet are firmly planted elsewhere - in Greek cultural and philosophical ideas of living and acting well.
J. L. Ackrill, Aristotle on Eudaimonia, London, 1975.
S. R. L. Clark, Aristotle's Man, Oxford, 1975.
A. Kenny, The Aristotelian Ethics, Oxford, 1978.