since/as?

[palinkasocsi]

I wonder if the conjunction 'as' can be used in place of 'since':

The theory is assailable since/as? it does not define ...

The thing is that I want something else instead of 'since'.

Many thanks.

[Snowcake]

Yes, they are interchangeable.

[Soup]

Both work. You could also use because.

[palinkasocsi]

how about:

for it does not define ... ?

[Soup]

For works too.

[palinkasocsi]

One last thing:

I'm just wondering whether I should put a comma before as/for or no comma would also do:

The theory is assailable, as/for it does not define ... properly.

[Soup]

No comma required. Note that for is somewhat rather formal.