I can't make Descartes fit the wordplay (or what I presume is the wordplay), darn it.

Pale you lamented, or so I theorize.

(9 letters)

 

_ o _ _ _ _ _ _ e

postulate?

Yes twyngwyn.

 

All yours.

this vessel sounds like cover stocks (9)

this vessel sounds like cover stocks (9)

 

_a____a__

this vessel sounds like cover stocks (9)

 

_a_i__a__

Capillary

yes  nfs, over to you

Quickie.

 

I hear the 12th and the 15th had five in a row; how grand.

(8 letters)