Since when does philosophy only need to be self-consistent?

I don't think you know what philosophy is.

Really? Name three other constraints on philosophy.

Note: They must apply to philosophers of antiquity and modularity, secular and of faith, eastern and western, human and non human etc.

You said that philosophy is only limited by the need to be internally consistent.

Well, for one, religious philosophy is often not internally consistent. Same for eastern philosophy. And most of the history of western philosophy, for that matter. So even your one criterion doesn't work when you force it to be universally applied to everything that's ever been given the title of philosophy.

And that's the problem with your statement. It takes the broadest possible subject in the history of man and makes a generalization about it that at best applies to some small sub-set and at worst applies to absolutely nothing.

What you are talking about is the validity of a philosophical argument. But just about every discipline in philosophy is also concerned with the soundness of the argument.

Even things like ontology or metaphysics are concerned with correlating their arguments with the way things actually are in the world.

Otherwise, all philosophical discourse would occur in symbols. But instead, the factual accuracy of the argument's constituent premises is also important.

So epistemology, ethics, political philosophy, aesthetics, philosophy of law, religion, mathematics, and language... 100% of these things are concerned with much more than being internally consistent.

Subset's of philosophy are often defined by their individual constraints. Huge areas are devoted to various assumptions such as "the bible is literally accurate" or "how people actually behave" (descriptive ethics), but the only thing they all have in common is a drive for reasonable levels of consistency. Taken to an extreme you end up with Math in all it's glory, but a complete lack of such consistency results in meaningless gibberish.

Consider the amount of effort spent to explain evil in a world created by a good, perfect, and all powerful god. Or the winding paths to define "truth" without creating a tautology etc etc. IMO, Philosophy sit's in the middle ground between religion which is happy to make inconsistent things up, math which requires self consistency, and science which must be grounded in reality.

huh? define a philosophical constraint and i'll undefine it for you... i believe the import is that it helps us come to terms with our humanity, which has no formal definition, by definition

mathematics certainly informs philosophy, the most pertinent example that comes to mind is godel on the works of wittgenstein... if you look at philosophy post godel/wittgenstein it has become continental philosophy (analytically formed 'novels') and analytic philosophy (which informs the impact of logic on natural language)...

each of these activities carries as much or as little weight as you would like to give it... but conservative thinkers might say the same of even pure sciences - are we really better off with all the devices/distractions of modern life?