Most religions on earth claim that God is formless, and yet, all-powerful/omnipotent. Logic says, the moment our mind accepts that God cannot have form, we reduce at least one of His powers. Ancient wisdom stresses that all forms are indeed God's own forms - which tentamounts to essentially being formless. Yet, it lists 330 million functional forms of God (Raghunaath temple in Jammu, India clearly shows them physically).
Srimad Bhagwad Gita, the only scripture that describes God in first person with logical reasoning, dwells on this point. Gita certifies that worship of God in form or formless, invariable reaches God. At the same time, Gita asserts that all selfless-work,worship, meditation, perseverence, and penance - by thought, word and action - is indeed worship of God and that it MUST be dedicated to God with love. Thus, dedication can be done only by sharing fruit of actions with all beings with love - in line with the principle: 'all beings are one family or Vasudev kutumbkam' - share with friends, enemies and strangers alike (like our stomach shares food with all body organs and cells). Dedication of karma to formless God is thus very difficult for everyone to achieve: asserts Gita.
An amicable method of dedication of all activity of life on earth to God - the real dooer/'karta-purukh' is through an ETERNAL form of God, if any. Forms of All God's avatars including Krishna Himself, great teachers and religious guides are not eternal in their respective forms and cannot, therefore, be worshipped for eternal bliss.
In Gita, this riddle - which form to worship - was dealt with at length, as the ardent devotee represented in Arjun was a great thinker and questioner. After teaching vividly the code of ethics and conduct for man on earth, the brilliant teacher in Krishna, revealed Arjun (and few others, committed to Truth) a unique un-matched COSMIC/'BRAHM' experience of God revealing light of uncountable suns shining together (something like science calls, big-bang). From that brilliance appeared innumerable forms (pleaseant/unpleasant) all-fusing into one Virat form. Seeing Arjun scared to death, a pleasant smiling, loving and blessing Vishnu-form appeared and Arjun was enlightened to see that and requested again and again to see this form and, God obliged him and advised that, this Vishnu/Hari form can be worshipped as complete/'Purna' God or at par with Absolute "Par-Brahm-Parmeshwar' or "Param-Brahm". Krishna also made it clear that this 'knowledge of knowledge' is highly confidential, even to demigods and angels because they do not surrender there false ego of indivdualistic existence. Somuch so, egoistic king, Dhritrashtra, refused to accept this God's wisdom, despite being specially made available to him through his rath-driver, Sanjay and thus suffered extremely heavy losses.
Our own nature is such that we always show our smiling and pleasant face as acceptable representative of all our important body parts including brain, heart, arms, feet etc. Thus Gita advises that Lord Vishnu can be worshipped as representing the face of centre-sanctorum of infinite God for eternal bliss. Other parts (demigods,angels, etc) of God are only functional specializations for fulfilling temporary desires within the realm of perishable creation. Even prominent parts of Virat, thus change their forms upon being worshipped for bliss e.g. Mahadev becomes "lingam", Brahmaji shows ageing with white beard, Ma Shakti turns into Vashnavi/Durga, Ma Saraswati/knowledge disppears into realization, Lord Ganesh is resurrected as elephant-headed, Shiva-incarnate assumes monkey-headed Hanuman-form, etc. Thus Gita concludes: Complete God can be worshipped for eternal bliss, as clout of all powers and energies as a bright luminous sphere "Shaligram" or God's own favorite human face Lord Vishnu, depending on person's intellecutual calibre. Saints like Guru Nanak thus declared "Poora Prabhu araadhiaye, Poore de gun gai" meaning worhip only COMPLETE GOD for achieving bliss.
