Part of the Numbers in Thelema series.
From Liber L vel Legis
Sub figura XXXI:
"None, breathed the light, faint & faery, of
the stars, and two. For I am divided
for love's sake, for the chance of union."
"The Perfect and the Perfect are one
Perfect and not two; nay, are none!
Nothing is a secret key of this law"
The formula 0=2 represents a cycle frequently used to describe the mystical result of yoga or sex magick. It may properly be linked to the concept of yin and yang.
The first half of the cycle deals with ascent from the normal to the supernal: the normal result of forcing two equal and opposite things to combine is annihilation of both values. This results in a zero sum.
The other half of the cycle is less readily understood as it deals with the descent from the supernal to the normal: the supernal result of a true union (through love) restores the values to the annihilated opposites, but in doing so sums the absolute values (http://en.wikipedia.org/wiki/Absolute_value). This results in a sum of two.
A means of expressing this is as a pair of equations, which may demonstrate the change of perspective expressed in Liber Legis.
0 = (+1) + (-1) (combination of the original values of polar opposites resulting in annihilation of its members)
|+1| + |-1| = 2 (union of the absolute values of polar opposites resulting in the restoration of the members)
0 = (+1) + (-1) «=» |+1| + |-1| = 2
This is actually an oversimplification of the actual underlying set theory (http://en.wikipedia.org/wiki/Set_theory), but the above should be sufficient for most purposes of understanding.