Andreas van Cranenburgh

1. The general argumentative strategy seems to be to show
that there is a tension between the idea that meaning is
defined by use, which is extended in time, and our intuitive
feeling of being able to grasp meaning in a flash, be it the
meaning of `cube' or how to continue a number sequence. But
a picture or something like it cannot determine the
application of a word, because one needs a specific method
of projection to compare it to possible instances.
Furthermore, at any point in a number sequence it can be
continued in an infinity of ways. If we accept that
interpretations of rules are in the mind, then generally we
can always fit one thing to another, in some way or another,
ie., any behavior can be construed to accord to any rule.
Wittgenstein raises issues about following a rule for
applying a word in an unbounded number of cases, and says
that such a rule cannot be present before someone's mind and
determine in advance how the word should be applied. This
shows that Wittgenstein is an anti-realist when it comes to
rules. 

The consequence for interpretation is that it is never
possible to demonstrate the correctness of an
interpretation. Grasping something in a flash -- "now I've
got it" -- can be a deceptive experience. There will always
be a connection between use and the rules that guide use,
because without such a connection meaning would not
function; however, this connection is forever beyond our
grasp. 

2. On certainty 27 "[...] it would contain the expression
`in normal circumstances'". As a presupposition for a rule
one must know the normal circumstances in which it can be
applied.

On certainty 34 alludes to whether students are explicitly
told to trust calculations by the teacher, or to trust their
own senses. These things should rather be presupposed than
taught.

On certainty 44-45 mentions that correctly calculating is
not the result of a rule, but by learning about the nature
of calculating.

The relation with Davidson seems to be that these
presuppositions are very similar to the principle of
charity. All the statements that cannot conceivably be
doubted are like the common ground necessary before radical
interpretation is possible according to Davidson.

3.
The notion of an institution indeed presupposes a community,
because it is in the sanctioning through usage and
application that the institution comes to be. 

For Wittgenstein the emphasis for practice is on activities
rather than objects. From practice the meaning of words and
tools emerge. Both anti-essentialism and anti-pschylogism
characterize his position on practices.  For example a move
in a game of chess doesn't consist of some particular mental
state, nor is it about the movement of the physical piece;
rather it is about how the action ties in with the practice
of playing games of chess and solving chess problems.

Both Wittgenstein and Heidegger focus on practices and
challenge representationalist accounts of cognition. Also,
since both deny the existence of forms and categories of
pure reason, they hold that our starting point must be
desctriptions of everyday situations in the world.
Wittgenstein, however, with his examples from games, seems
to lay more emphasis on social interaction than Heidegger.
Consequently, the ready-to-hand is not as contemplative as
Wittgenstein's practice, rather it is an absorbed coping,
where the moves in a Wittgeinsteinian game can be reflective
or even calculated.
Furthermore it seems that Heidegger's ready-to-hand is
always related to Dasein -- something is ready-to-hand for
a specfic Dasein, say whether a hammer is within reach.
Wittgenstein's practice, on the other hand, belongs to a
community, and the practice of hammering is not affected by
the presence or absence of particular hammers.