The Rambam is widely perceived as an Aristotelian Rationalist.
And yet, in his Sefer Hamtzvot - Lav 287 re: the testimony of relatives - the Rambam states:
"Even if a Father were to testify against his son, we do not accept it. It is a G'zeirat Hakkatuv "she'ein Lah Ta'am K'lal"
So even for the Rambam, not every case or Mitzvah has a rational explanation, nor can it be "rationalized".