 Note that Leibniz here reaffirms that we are aware only of the perceptions that are “sufficiently distinctive” or are “forceful enough.” This suggests a certain level of perceptual distinctness or force that will “make themselves felt.” As in the case of the mill—you move in next door to the mill and can’t sleep because of the noise. But, over time, you become accustomed to the sound of the mill and no longer notice it. It is this sort of phenomenological fact, which we can all recognize, that Leibniz thinks he can explain in terms of the variations in perceptual distinctness. It’s not, as he says, that the noise no longer affects our sensory organs—the noise continues to be registered internally, but there is something about the lack of novelty that results in a transition in consciousness. We no longer notice the noise (or, at the very least, we don’t notice it nearly as much). What explains this? Leibniz thinks he can give a natural explanation of this in terms of the forcefulness of the impression. Somehow it becomes less forceful over time. (How does it do this? Leibniz doesn’t give us a full account here. This is where he thinks we will see the promise of his theory and then investigate the  causes.)[17] 