Shivoham is a state of divine being

Sri Adi Shankarachaarya does refer Aham as not the person which we refer as I or himself. "Mano buddhyahankaara chittaani Naaham Nacha Srotra Jihwe NaChaagraaNa Netre Nacha vyoma bhoomi na tejo na vaayuhu Chidananda Rupa Shivoham Shivoham" I’m not the mind, intelligence, emotion. I’m not the senses which perceives world. I’m not neither never ending Sky or earth or fire or wind. I’m that which exists in all of these beings as a backbone and responsible for their existence. I’m that Atma which is just form of Shiva and Nature of Shiva.

Shivoham is a state of being which is experienced by learned one or realized one. The one who realizes this is truly none other than Shiva. Because he is no more identifies himself as a person but pure consciousness or Atma. Shri Aadi Shankara refers Aham as True Nature of Himself which is Atma. He has realized this fact and conquered the all other philosophies with His Advaitha Philosophy at that time.

Vedas do not just declare Parameshwara to be supreme but also make a superlative statement saying that none is equal to Sri Rudra. The Shiva Sankalpa Suktam itself pretty much tells us that none is superior to Ishana. ?????? ?????? ????????? ?????????? ????? ????? ? ?????????? ????? ?????????????? ???? ??????????????????? ? 18 Greater than the great is Brahma, greater than the great Brahma is Vishnu. Greater than the greater Vishnu is Isha (Shiva). May my thoughts be filled with Shiva. - Rig Veda Khila, Shiva Sankalpa Suktam, 18th Mantra.

Even the Rig Veda itself states that none is mightier than Sri Rudra: ??????????????? ????????? ?????????????????? ?????? ???????????? ? ???????????? ?????? ???????????? ? ?? ?????? ?????? ????????? ? ?.???.?? Worthy, thou carriest thy bow and arrows, worthy, thy manyhued and honoured necklace. Worthy, thou cuttest here each fiend to pieces: a mightier than thou there is not, Rudra. - Rig Veda, Mandala 2, 33rd Suktam. Sri Rudra is also called the Lord of Yagnas, Mantras, and medicines. ????????? ????????? ??????? ??????????? ? ????????? ???????????? ? ?.???.?? To Rudra Lord of sacrifice, of hymns and balmy medicines, We pray for joy and health and strength. - Rig Veda, Mandala 1, 43rd Suktam.

Moreover, many Shaiva sampradaayas also consider Vishnu a “jiva”. But by “jiva”, we do not mean that Shiva is an ordinary living entity like us. The reason is: anything other than Eeshwara (Vishnu), is considered a jiva. Hence, eternity is associated with Hari alone, and no one else, because every other entity eventually merges into Vishnu and reappears again, later. The main reason for considering Shiva a jiva, is because the Paancharaatra aagamas say so. Here is a random online post by a Sri Vaishnava, where he mentions Shiva to be a jiva: But to declare that there is no one superior to Shiva would violate Ramanujacharya's most fundamental beliefs. For the Pancharatra Agamas state that there is someone superior to Shiva; Shiva is a Jiva who is the son of Brahma, and the being who dwells in Shiva's heart is Vishnu's Vyuha form Sankarshana, who emerges from Vyuha Vasudeva who lies down in the ocean of milk, who emerges from Para Vasudeva, the supreme Vishnu.

Source: Why did Sri Ramanuja refuse to hail Shiva? What was the need to prove that Vishnu is the one true God? The Shrimad Bhaagavatam confirms this: ?????????: ??????????????????????????????? ?????????????????????????????? ??????? ?????? ??????? ?????????????: ????????????????????????????? ???????????????????? ?? ??-????? ? ?? ? In Ilāv?ta-var?a, Lord ?iva is always encircled by ten billion maidservants of Goddess Durgā, who minister to him. The quadruple expansion of the Supreme Lord is composed of Vāsudeva, Pradyumna, Aniruddha and Sa?kar?a?a. Sa?kar?a?a, the fourth expansion, is certainly transcendental, but because His activities of destruction in the material world are in the mode of ignorance, He is known as tāmasī, the Lord’s form in the mode of ignorance. Lord ?iva knows that Sa?kar?a?a is the original cause of his own existence, and thus he always meditates upon Him in trance by chanting the following mantra. -Shrimad Bhaagavatam, Canto 5, Chapter 17, Shloka 16 So, this is because it is said so in the aagamas, the same aagamas, whose parts were rejected by Shripada Adi Shankaracharya.