God’s nature is incomprehensible to humans.
This dogma affirms that God is greater than anything we can think, say, or comprehend. His nature cannot be grasped by human reason, even though we can make true statements about Him through revelation.
We can speak of God—but never fully “understand” Him. He remains the absolute mystery—eternal, boundless, holy.
Source (Latin):
Pius IX, Constitutio dogmatica “Dei Filius”, Sessio III (April 24, 1870), Caput I. In: Acta Sanctae Sedis, Vol. III (1870), pp. 556–558.
Source (Systematic):
Denzinger-Schönmetzer DS 3001 / CCC Nos. 230–231