There are simply too many random factors: accidents, accidents of birth, accidents of things dropping on people's heads, illnesses, etc. We will never get to grade them, never get to grade people as they should.
Simplemente hay demasiados factores aleatorios: accidentes, accidentes de nacimiento, accidentes de cosas cayendo en la cabeza, enfermedades, etc. Nunca conseguiremos evaluarlos. Nunca evaluaremos a las personas como se debería.