I've been reading 'Aristotle: The desire to understand' by Jonathan
Lear. Reading even a few pages really tires me out but it has been
eye-opening. I knew nothing about Aristotle before but his vision
of what the world is like and how people fit into it is very
appealing; the world is understandable, and people are able to
understand it.

Plato's forms are abstract perfect things existing in an ideal world
outside ours, but Aristotle's forms exist in our world. For Plato
a squirrel in our world is a shadow of an ideal squirrel in the
separate ideal world, but for  Aristotle a squirrel is a composite
of matter and form, with the form governing the matter. For Aristotle
form is responsible for the structure and change of matter, for
example driving the baby squirrel to develop into an adult squirrel.
There is one form per species, so there is only one squirrel form
but it's embodied in many material squirrels.

Reading about Aristotle's forms I was strongly reminded of the
wavefunction; it is a non-material, real thing that governs matter,
and there is but one wavefunction for the world's many electrons.
And the wavefunction makes electrons understandable; I think it
could legitimately be called electrons' inner principle of change,
which is what Aristotle's forms are. Not that I think Aristotle's
forms are exactly the same thing as wavefunctions, just that they
have some analogous features which are interesting to me.

Aristotle's picture of what happens when we think about a squirrel
is just fantastic. The form of the squirrel actually enters our
mind, and our mind becomes the squirrel form (just at a higher level
than it existed in the squirrel, just like the form in the adult
squirrel is at a higher level than the form in a squirrel embryo).
Not that our brain is converted into squirrel-matter! It is just
squirrel-form, not any squirrel-matter, that our mind becomes when
we contemplate squirrels. So rather than saying 'we think about the
squirrel' we could well say that 'we think the squirrel', or just
as well - since our mind becomes the squirrel form - that 'the
squirrel thinks us'! I don't believe this but I do find it a very
vivid image, and as a metaphor I do like our minds taking on the
form of what we think about. That the structure of our ideas might
reflect the structure of what they are ideas about is quite interesting
I think.

The book only has a little bit on Aristotle's philosophy of mathematics
but it sounds very interesting to me. Looking at geometry, rather
than studying ideal triangles in a separate Platonic world, Aristotle
says we are studying the properties that actual physical triangles
purely because they are triangles. I like the sound of this.
Aristotle's vs Plato's take seems related to the physics-first or
geometry-first ways of looking at geometry in relativity (i.e.
whether it's the electromagnetic properties of rods that explain
why the metric is useful or whether the metric explains why rods
behave as they do).

Aristotle's ethics also seems very practical - it seems to involve
trying to act appropriately in the given situation rather than hard
and fast rules, which I like. Also it emphasises that we pick up
virtues/excellences by making a habit of doing virtuous/excellent
things - this has encouraged me to try to make a habit of doing
physics and practicing the guitar (I wonder if it'll work...). One
thing which I struggled with is Aristotle saying that we ultimately
have to choose between the ethical life (contributing to society
etc) and the life of understanding (which sounds like withdrawing
from society and spending all your time thinking about things). I
hope it's possible to do a little bit of both, although thinking
about it right now I don't do much of either.