For every rule, there is an exception.

Now, the said statement above is, in itself, a rule.

Question: What is its exception?

Ergo, There should be an exception to the rule,

e.g.- there is no exception to the rule –

However, by excepting something - It does not except anything.

Hence: there is a rule that has no exception which is in itself accepts an exception.

That is the absolute rule you have been looking for.

Otherwise stated- it is the absolute rule by excepting everything including itself. Paradoxically, it excepts nothing by excepting everything.

The rule is that “for every rule there is an exception”. 

Applying the rule- that there must be exception, hence: an as exception to the rule, that is: “A rule without exception”, which is in itself an exception to the rule, hence giving credence that indeed there is an exception to every rule.

Otherwise stated, an exception to the exception of the rule is the rule itself.