Brentano's views on the ontological status of sensations have been almost completely ignored in the scholarly debate on his ontology of the mind. This is rather unfortunate, because such views shed light on the evolution of Brentano's perspective. In his "Psychology" (1874), Brentano claimed that all intentional objects both sensible, and intellectual share the same ontological nature. Yet he later dismissed this whole doctrine and began to distinguish rigorously between sensible and noetic conscience. I argue that this change was due to Brentano's views about the neurophysiology of human sensibility. After a long confrontation with Fechner, Brentano eventually embraced Helmholtz's idea of neural «specific energies» and shaped his newly developed doctrine of sensible qualities in accordance with it. Far from letting his ontology be driven by what he called «genetic psychology», Brentano was nevertheless prudent enough to develop his theories so that any contradiction with ascertained scientific facts could be avoided.