Two questions we might ask ...
Are patterns real?
There are several suggestions for the reality of pattern like things
in the eye of the beholder
Patterns are wherever we as conscious, sentient beings interpret them to be
problem : what about us? We might like to try to use patterns in an explanation of we conscious, sentient beings. But then the problem either becomes circular :
Q : What are patterns? A : what we interpret them to be
Q : which things count as valid interpretters? A : things which have a particular, personlike, pattern
So we end up wondering how the whole thing gets of the ground. And if we don't have an answer, isn't it just a kind of relativism?
Patterns as information saving summaries
Wherever we can use reference to the pattern as an information saving summary in describing the world, there is a real pattern.
problem : What's information? Is it defined in terms of us and our expectations ? (Could lead via another usdependent cirularity to relativism)
: There is a mathematical theory of information. Look for "A Mathematical Theory of Information" by Shanon. ZbigniewLukasiak
:: Yes, but that defines it in terms of surprise to the receiver (ie. us)  PhilJones
problem : How do we measure it? Is it something like KolmogorovComplexity, and does that depend on an arbitrary number base? If so, aren't we again falling back into some kind of relativism? (ie. patterns are relative to the arbitrary number base chosen)
The second question, the epistemological one
What kind of activity is the search for, and documentation of patterns? Is it just some kind of annecdotal story telling. "hey, we tend to like cities with this kind of scalefree structure?" Is it a kind of science? Is it maths? "I'm studying general ReactionDiffusion patterns in general using iterative methods on my computer."
To read ...
See also :

Comment on ProcessPatterns from TeleDyn : (should http://www.teledyn.com/mt/archives/002146.html (should be connected with / moved to OnRhetoric and OnInterventions)
CategoryScience