Just formatting a column in Excel using VBA I thought I'd just do it quick and replace each cell with itself formatted. Just checking the logic to make sure it would do what I thought it would do I found myself thinking that the value of the cell would be copied to memory, formatted and then copied back into the cell. This is the behind the scenes computation of this code:
Cell(2,2) = CDate(Cell(2,2))
Yet the code looks like it implies a self-reference where the contents of the cell is made the same as a function applied to the contents of the cell. A more absurd example would be:
Cell(2,2) = Cell(2,2) + 1
Why don't computers ever end up with a paradox here? It's not really a question because everyone knows that the "=" sign is not a statement of equality but of assignment. The contents of Cell(2,2) are to-be-given the value of themselves + 1.
But semiotically it is interesting that we use the "=" sign here. Better languages than VB have three signs: = for assigment (add 1 to y and put it in y), == for equality (are they the same), and := for definition (resolve the value of y=y+1) . Yet they all recognise these three quite different things as belonging to the family of =.
1) Cell(2,2) = Cell(2,2) + 1 is an instruction
2) Cell(2,2) == Cell(2,2) + 1 is always false
3) Cell(2,2) := Cell(2,2) + 1 is the contradiction! It actually ends up in a recursive loop.
Now it is (3) which is the problem for logic. Loops I have suggested before are the computational symptoms of the same problem as contradictions and paradox in logic. Where a paradox occurs in logic, a computer hangs in a loop. What Godel discovered by contradiction in his famous statement, Turing discovered in his non-halting looping programs. There is a deep connection. I am just starting to read Chaitin on this; looks like it will be very promising.
So what the SRH is crudely saying is that a definition (:=) can't be constructed from itself i.e. impredicativity.
Iterative processes and self-organising systems are a different type of equality (=). They are not created from "themselves" but from their output. Obviously if they were created from themselves then they could never change because they would always be themselves. The equation y = (y ^ 2 - 1) / -3 iterates to its roots -(3 +/- root(13))/2 for certain starting values of y. The complexity of successive applications of a function is extraordinary in many cases. Unlike a snooker ball bouncing around a snooker table where very quickly the ball ends up following a repetitive trajectory, with relatively simple function systems, paths can be created which never repeat (except for precision rounding errors)! Link here to the Lorenz curve. Fractals etc illustrate the enormous hidden structure to iterative/recursive procedures (things built from identical copies of themselves). But the point is that this is all a distraction from the SRH issue of things being built from actually themselves, rather than copies and things that are similar.
An issue here is that of identity. A floor can be completely tiled in repeating shapes. This is of interest to the builder because a simple production process specialised to a few shapes can create tiles that are guaranteed to fit together anywhere and cover any expanse of floor. A wonderful example of mass production. Yet this simplicity ought not be misunderstood as Penrose discovered with just 4 types of tile it is possible to tile a floor without ever repeating. Apparent infinite complexity from a very finite set of building blocks. Shades of the Lorenz curve here where something built from simple components iteratively never repeats. Yet each tile is intellectually the same as its type (same angles and lengths of side) each individual tile (token) is necessarily different. A floor cannot be covered by one tile. It is exactly the interaction of many tiles that covers the floor. The patterns that arise can only occur between tiles, they are not intrinsic to any particular tile. Indeed to even "be" a tile requires that we have seen other tiles before, are familiar with the culture of tiling, and speak this language where they are understood as tiles. A single tile all on its own in the universe is more than useless for covering a floor, it doesn't even get given a name by the people of that universe.
SRH only applies to things built from their own token. Now in maths, unlike with the building trade, this is far from clear.
y := y + 1
There are actually two marks on the page here corresponding to the single letter 'y'. If there were not two marks we would not be able to write this equation. Once read however we understand that the two names, 'y' on the left and 'y' on the right, are supposed to be names of the same thing.
In the case above
y := (y ^ 2 - 1) / -3
are we to understand that the thing 'y' has two possible stable values (a superposition) so to speak. Very quantum physics ;-) This finding of multiple possible values to fit incomplete conditions seems to be me to be more a feature of the language of maths than anything "real". We don't think that some mysterious entity is lying here under the page with two values.
In
y = y + 1
They are names of the same 'storage place' or 'variable' which can have any value. Unlike above the value is not what is named by 'y'. Strictly the two variables should have different names e.g. y(n+1) = y(n) + 1 and a starting value given also y(0) = 0.5. As a function the relationship is a mapping of left and right hand sets. In this case it forms a zig-zag relationship through all members of the sets.
Also things that are defined in terms of themselves can't change because they can only ever be themselves. To change we need to become something else. This means that things that are defined in terms of themselves are both immortal and can't be created. SO impredicativity is violated in immortal, a priori, analyic, uncreated entities. This means obviously that you cannot "build" or "create" something using itself, you can only support it. This is the castle in the sky with its foundations built upon its walls.
So the only problem that SRH is referring to is the idea that something is built with exactly itself. It is perhaps an ontological problem as much as anything.
Husband is jailed for ordering machete murder | UK news | The Guardian
Women are choosy - look who they choose. This hit the papers today, several hours after I posted my headline. Can you understand my bemusement/bewilderment/bi