52 Therefore, in the discourse we have expounded above, He had borne witness to the unity of His nature with the Father's: He that has seen Me, has seen the Father also : The Father is in Me, and I in the Father These two passages perfectly agree, since Both Persons are of equal nature; to behold the Son is the same as to behold the Father; that the One abides in the One shows that They are inseparable. And, lest they should misunderstand Him, as though when they beheld His body, they beheld the Father in Him, He had added, Believe Me, that I am in the Father and the Father in Me: or else believe Me for the very works' sake. His power belonged to His nature, and His working was the exercise of that power; in the exercise of that power, then, they might recognise in Him the unity with the Father's nature.
In proportion as any one recognised Him to be God in the power of His nature, he would come to know God the Father, present in that mighty nature. The Son, Who is equal with the Father, showed by His works that the Father could be seen in Him: in order that we, perceiving in the Son a nature like the Father's in its power, might know that in Father and Son there is no distinction of nature.
Source: On the Trinity (New Advent)