@user4550 you're swapping adjectives and nouns, and "much" applies differently.
"is as much" literally means "has an equal amount of", so the original sentence means "half philosophical and half scientific". It's fine as originally written.
When "much" is applied to a noun it is a VAGUE QUANTIFIER, you can substitute "a large amount". It applies to uncountable nouns (like "money"); countable nouns (like "dollars") would use "many" instead of "much".
When "much" is referencing an adjective it is an AMPLIFIER, and an additional modifier is needed (like "more" or "less", or changing "cute" to "cuter") to indicate the direction being amplified. "Much" actually applies to the modifier.
With the adjective you can say:
Twice as extravagant.
Much more extravagant.
You cannot say "a large amount of extravagant"
but you can say "a large amount MORE extravagant"
Changing the adjective to a noun you can say:
Twice the extravagance.
Much more extravagance.
Twice as much extravagance.
you can even say "with much extravagance".
a large amount of extravagance.