sarvametadritam manye yanmaam vadasi keshava |
na hi te bhagavanvyaktim vidurdevaa na daanavaahaa || 14 ||

What you are speaking to me, O Keshava, I acknowledge all this to be true. For O Lord, neither the deities nor the demons know your manifestation.
sarvam : all
etat : this
ritam : truth
manye : acknowledge
yat : whatever
maam : to me
vadasi : speak
keshava : O Keshava
na : neither
hi : for
te : to you
bhagavan : O Lord
vyaktim : manifestation
viduhu : know
devaaha : deities
na : nor
daanavaahaa : demons
Since the start of the Gita, we have seen Arjuna speak whenever he has a doubt or needs further clarification. With this shloka, Arjuna acknowledges that he has completely understood the true nature of Ishvara since the knowledge is coming from the source, from Ishvara himself.
It is interesting to note the use of the name “Keshava” to refer to Shri Krishna. “Ka” represents Lord Brahma and “Isha” represents Lord Shiva. So Keshava is the one who harmonizes the powers of creation and destruction. In other words, Ishvara creates, sustains and dissolves the universe of names and forms.
Since Ishvara is the origin of everything, Arjuna says that no deity, human or demon can claim to know Ishvara in totality because Ishvara came before any of them. Another interpretation of this statement is that no sense organ such as the eye or ear can claim to know Ishvara. Unlike worldly knowledge about objects, the knowledge of Ishvara can only be known as a subject. Tulsidas says this poetically in the Tulsi Ramayana : “Jaanat tumahi tumahi hui jaayi”. One who knows you becomes you. All sense of individuality, the sense of I, the subject, goes away when one merges into Ishvara.
So then, if no deity, human or demon can know Ishvara, who can? Arjuna gives the answer in the next shloka.