1.
The affinity argument (Phaedo
77d-80c).
See
the text.
I got the following formulation of the affinity argument from Samuel C. Rickless' page here. Rickless teaches at UCSD.
Noncomposite things
are indissoluble.
Things that always remain the same in the same state are most likely noncomposite.
Forms always remain the same in the same state.
Sensible things never remain the same in the same state.
Forms are invisible.
Sensible things are visible.
So, invisible things always remain the same in the same state, and
visible things never remain the same in the same state.
The soul is invisible.
So the soul is indissoluble.
When the soul investigates things that remain the same in the same state,
it too remains the same in the same state.
The soul investigates the Forms.
So, the soul is indissoluble.
The nature of the divine is to rule and lead.
The nature of the soul is to rule and lead (the body).
If X is F and Y is F, then X resembles Y.
So, the soul resembles the divine.
The divine is indissoluble.
If X resembles Y and Y is G, then X is G.
So the soul is indissoluble.
2.
The "use" argument (Alcibiades
I, 129B-130C)
A
user differs from what is used.
A
human uses his/her body.
Therefore
a human must be different from the body.
A
person is either body, soul, or a combination.
A
person is not body (by the argument above).
A
person is not a combination (by argument above)
Therefore,
a person is soul.
3.
The "proper work" argument in Republic
352D-354A
The
proper work or function of a thing is that which it only does, or it does best.
Whatever
operates does its work well by virtue, and badly by defect or vice.
The
proper function of soul is reason, management, rule, deliberation, AND life
(soul is the "vital principle").
Therefore
the virtue of the soul is to reason, manage, rule, deliberate well.
Corollary:
virtuous souls also exercise the other proper function of soul, namely, they
LIVE (as long as they reason, manage, etc.)
4.
The recollection argument in Meno
81B-E, 85B-86B
We
find ourselves with knowledge that is unchanging (e.g., math).
World
of the senses is always changing.
Therefore
our knowledge of the unchanging can't come from the world of the senses.
Knowledge
comes either from senses or it is innate (inborn).
Our
knowledge of the unchanging doesn't come from the senses.
Therefore
this knowledge must be innate.
Knowledge
requires a knower.
Therefore,
if innate knowledge exists, a knower of this innate knowledge must also exist.
A
knower must exist in order to acquire knowledge.
Therefore,
knowers of innate knowledge must exist before they are born, in order to
acquire the knowledge they possess at birth.
It
is reasonable to assume that if we lived before birth, we will continue to live
after death.
Another
version in Phaedo (74E-75E, 76D-E):
We
know with certainty that things in the world of the senses are not perfect:
e.g., we know beautiful things are not absolutely beautiful.
We
could not have this certainty if we did not already know what absolute beauty
is.
Therefore
we must know absolute beauty innately.
Therefore
we must have lived before birth.
5.
The "cycle of opposites" argument
In
nature we observe cycles of opposites. Hot things become cold, and then cold
things can become hot; living things become dead, and then life emerges from
dead things, etc. (like yin-yang).
Therefore
it is reasonable to suppose that when we die, we will be transformed into
something alive.
6.
The argument why soul must be something, and not just a "harmony" (Phaedo 85D-86D, 91E-92C, 94D-94E)
There
are too many relevant differences between soul and harmony:
· Soul pre-exists. (This is
supposedly established by the previous arguments.) Harmony doesn't pre-exist.
· Unlike harmony, soul leads,
moves, is active.
· Harmony can be greater or
less, but not soul.
· Souls can be more or less
virtuous or wicked, but these terms do not apply to harmony.
· If the soul were harmony, all
souls would be equally good, which is absurd.
Therefore,
the soul must be a substance, and "far more divine" than harmony.