One of the main causes of our mind's lack of application to abstract truths is that we view them as remote, whereas things much closer to the mind are constantly being presented to it. The mind's close attention, as it were, brings the ideas of objects it is attending to much closer, but it often happens that when one is intent upon metaphysical speculations, one is distracted from them because some sensation crops up in the soul that is, as it were, still closer to it than its ideas....The buzzing of a fly, or some other slight noise -- given that it is communicated to the main part of the brain so that the soul may perceive it -- in spite of our resistance is capable of preventing us from thinking about the loftiest abstract truths, because no abstract idea modifies the soul as sensations do.
Malebranche, The Search After Truth 3.1.4 (LO 213).
