Zimmermann also declares that the compilers of the "Tathagātagarbha Sūtra" "did not hesitate to attribute an obviously substantialist notion to the buddha-nature of living beings," and notes the total lack of evident interest in this sutra for any ideas of "emptiness" ("śūnyatā"): "Throughout the whole "Tathagātagarbha Sūtra" the term "śūnyatā" does not even appear once, nor does the general drift of the "TGS" somehow imply the notion of śūnyatā as its hidden foundation. On the contrary, the sutra uses very positive and substantialist terms to describe the nature of living beings.' Also, writing on the diverse understandings of Tathāgatagarbha doctrine, Jamie Hubbard comments on how some scholars see a tendency towards monism in the Tathāgatagarbha tendency which Japanese scholar Matsumoto castigates as non-Buddhist. Hubbard comments: