We should understand that Bhagavan, God, is superior to all. It is a wonder unexplainable. It is a wonder or adbutam अद्भुतं, in Sanskrit [arputham அற்புதம் in Tamil]. The Lord as Sri Adbhuta Narayana [ஸ்ரீ அற்புத நாராயணன்] is gracing in Thirukkadithanam [திருக் கடித்தானம்]. We have come to this Kshetram in Kerala. As usual, nature is bountiful in this place, also. We first see the temple pond, Bhoomi Theertham. Vimanam is Punyakoti Vimanam. The Lord is Sri Adhbhuta Narayana and Sri Thayar is Sri Karpakavalli Thayar [ஸ்ரீ கற்பகவல்லி தாயார்]. Nammalwar had dedicated 11 pasurams [8.6] in Thiruvaimozhi, to this Lord here. In the pasuram 8.6.10, Alwar says 'arputhan narayanan ari vamanan, nirppadhu mevi, iruppadhu en nenjagam [அற்புதன் நாராயணன் அரி வாமனன், நிற்பது மேவி, இருப்பது என் நெஞ்சகம்!]'. He describes Thirukkaditthanam as surrounded by orchard of Karpaka trees! Even now, the pleasant greenary, beautiful pond and other natural surroundings, induce Bhakti in Him. This temple is opened as early as 4:30 A.M. One can have a bath in the pond and then worship the Lord and get peace of mind. As in all Kerala temples, the cleanliness in the temple, bathing in the pond, not chatting inside temple, non-usage of electric lamps inside temple, etc., can be seen here also.
Nammalwar says why the Lord here is Adbhutan or Wonder. The Lord is Sri Narayana, Sri Hari and Sri Vamana. Narayana indicates the quality vatsalyam or rejoicing over blemishes of the devotees. The faults of the devotees are pleasing to Him [like the dirt on a calf is tasty for the cow!]. This is an abnormal quality. We never praise others' mistakes! So, this quality is a wonder in Him. Next, Hari means destroying the enemies. Inherent enemies in us, like jealousy, anger, lust, ego,etc., are destroyed by the Lord. This is the second wonder. Finally, as Vamana, the Dwarf, to get back the lost Kingdom of Indra, He, Who is used to grant profusely, begged. This is also a wonder. Thus He proved to be a wonder as Narayana, as Hari and as Vamana! Alwar thus establishes the Lord as Wonder or Adbhuta! In the sloka 17, we are to see, the Lord tells that He is Paramatma and He is Purushottama. In slokas 17, 18 and 19, we are to see Three concepts, the Lord telling Arjuna. In sloka 17, He is to establish that He was Purushottama, from chosen reasons. Therefore, He is the main theme in Vedas and Puranas/Itihasas, the Lord tells in sloka 18. Again, therefore, Arjuna [as also all of us] should worship only Him, the Purushottama, the Lord tells in sloka 19. Thus He reasons out to say He was Purushottama, and hence He was the One described in Vedas and Puranas, and therefore, we all have to worship and surrender unto Him only. Now sloka 17:
uttamaḥ puruṣas tv anyaḥ paramātmety udāhṛtaḥ
yo lokatrayam āviśya bibharty avyaya īśvaraḥ 15.17
Uttama purusa = the Supreme entity, anya = is different. In the previous sloka, we saw two entities Kshara [bhaddhatma] and Akshara [Muktatma]. In this sloka He says that the Purushottama mentioned is different from Kshara and Akshara. Like we have degrees - good, better and best - here, the Lord is Utthama purusha. In Sanskrit it is purusha, uth purusha, utthara purusha and utthama purusha. Utthama purusha is the most superior of all and that is the Lord. The Lord is the most Superior to Bhaddhatma like us in this Universe amd also to Muktatma in Vaikuntam and in Kaivalya Moksham. Ity = this [utthama Purusha] is, udahrta = called, paramatma = Paramatma. Paramatma means none else above Him. In Upanishad it is told 'tasya sikhayamadye paramatma vyavastita: sa brahma, sa shiva:, sondra: sokshara: parama swarat'. Paramatma is in midst of the flame burning in the heart of all living beings. That Paramatma creates [this world] as [in the body of] lord Brahma; that Paramatma destroys [this world] as [in the body of] lord Shiva; that Paramatma is leader of Devas, as [in the body of] Indra; that Paramatma is as [in the body of] Muktatma! Ya = He Who, lokatrayam avisya = pervades all the Three entities. Here we should not interpret loka to mean world as then it will mean the Lord is pervading only the Three worlds, Bhu, Bhuva and Suvar Lokas, whereas the Lord pervades much more. So, loka trayam means the Three entities the Lord has been talking about - Achit, Bhaddhatma and Muktatma. Thus the Lord is pervading in all Achit, in all jeevatma we see in this Universe and in all muktatma, liberated from samsaram. Bibharti = sustains or supports, avyaya = indistructible or everlasting and without any deficiency, isvara = commander. Here the Lord is pervading everything both inside and outside. He is supporting everything from within and from without. Swam Adi Shankara says Iswara denotes Sriman Narayana only. Thus Sriman Narayana is Paramatma, because He commands everyone, He is everlasting, He is supporter of everything, pervading everything. Therefore, He is Purushottama, Who is different from and superior to Kshara and Akshara! By these reasons the Lord is Paramatma. Swami Koorattalwan says that in Shastras there are many common names like Brahmam, Atma, Sath, etc. There are also some special names like Shiva, Indra, Brahma, etc. All these common as well as special names denote only the Lord Sriman Narayana. Here we may get a doubt. In the sloka it is mentioned that Uttama Purusha is different. But nowhere in the sloka Sri Krishna tells that He was Paramatma! It looks a Third Person is referred to! But we should never forget the context in which Sri Krishna is telling Arjuna. If we read and interpret the sloka out of context, then it would lead to confusion. In sloka 15, Sri Krishna told Arjuna that He, Sri Krishna, was dwelling in the hearts of every living being and that He was responsible for memory, forgetfulness and Gyana. Therefore, since this sloka is to further explain His qualities, Paramatma refers to Sri Krishna only! Swami Alavandar in his Stotra Rathnam, asks Who was the Consort of Sri [Lakshmi]? Who was with lotus eyes? Who was embodiment of satva quality? Who was Purushottama? He answers that all these qualifications pertain only to Sriman Narayana. Also in Gitarta Sangraham, Swami Alavandar again says that since He was pervading all, supporting all, commanding all, Sri Krishna, the Lord was Paramatma and Purushottama. Alwar reiterates the same theme in His pasurams, and further says that such a great Purushottama lived in his heart!