We do not know the first Person unless we call Him Father

If only we ourselves loved Him, our heavenly Father, in a truly filial way! (Seraphim of Sarov)

“The name Father has thus been revealed to men . . . [but] what is this Father’s own Name? . . . No man knows God unless he confess Him as Father, Father of the Only-Begotten Son, and confess also the Son a Son by no partition or extension or procession, but born of Him, as Son of Father, ineffably and incomprehensibly” (Hilary of Poitiers, On the Trinity). Jesus Christ said, “Father, I have manifested Your Name unto men” (Jn 17:6) – “the work that the Lord came to do was not to enable you to recognize the omnipotence of God as Creator of all things, but to enable you to know Him as the Father of that Son Who addresses you . . . You hear the name Father; fix it in your mind that He is the Father . . . [because] the end and revelation of the Son is that you should know the Father . . . Remember that the revelation is not of the Father manifested as God, but of God manifested as the Father” (Hilary of Poitiers, On the Trinity).