In his Tattva-sutra, 30, Srila Bhativinoda Thakura writes: “An element that does not remain with the living entity in all circumstances is not eternal. The mind is a temporary faculty. In its constitutional position, the soul does not accept a material faculty. The mind is therefore a product of matter. However, since the mind is very subtle, it is superior to many material objects.” (from Sri Bhaktivinoda Vani Vaibhava, translated by Bhaumipati dasa, page 206)