The expression is attributed to Aristotle who articulated a belief that nature contains no vacuums because at the mere existence of a vacuum, the denser surrounding material continuum would immediately fill the void. He also argued against the void in a more abstract sense that by definition a void, itself, is nothing, and following Plato, nothing cannot rightly be said to exist. The idea was restated as “Natura abhorret vacuum” by François Rabelais (d. 1553), a French humanist and physician mainly remembered for his bawdy songs and poetry. The strictest criterion to define a vacuum is a region of space and time where all the components of the stress–energy tensor are zero. This means that this region is devoid of energy and momentum, and by consequence, it must be empty of particles and other physical fields (such as electromagnetism) that contain energy and momentum. But what does that have to do with today’s readings?
“When an unclean spirit goes out of someone, it roams through arid regions searching for rest but, finding none, it says, ‘I shall return to my home from which I came.’ But upon returning, it finds it swept clean and put in order. Then it goes and brings back seven other spirits more wicked than itself who move in and dwell there, and the last condition of that man is worse than the first.” (Luke 11:24-26)
Just because you rid yourself of sinful behavior doesn’t mean you’re in the clear. If you do not fill “the void” with prayer, spiritual practices, Scripture, and more – you are like a house swept clean and put in order. Satan peeks in, goes off and invites his friends. The ensuing “condition of that man is worse than the first.”
Apparently Satan also abhors a vacuum.