Achyutananda (and the other four saints) believed in a concept of God (Vishnu) as Shunya (emptiness, void, zero) called Shunya Purusha and/or Shunya Brahman. This shunya signifies a transcendental principle that eludes the conceptual nexus applied to human thinking as described in the Upanishads.
Philosophical Ideology of Achyutananda
nāhi tāhāra rūpa varṇa, adṛsha avarṇa tā cinha. tāhāku brahmā boli kahi, śūnya brahmhati se bolāi.
It has no shape, no colour, It is invisible and without a name This Brahman is called Shunya Brahman.
Achyutanada's culminating work is called the Shunya Samhita where he discusses this philosophy in depth.
śūnyara ākāra viira śūnyara vicāra, śūnye thāi dekha vīra e sacarācara. dekha e sacarācara śūnyare prakāsha, śūnyu ude hoicanti śūnyare vilāse.
Oh vira look at the shunya By placing yourself in shunya, And meditate on mahashunya, Shunya itself is the form, Ground of all discriminating knowledge. Look at the whole world from the pedestal of shunya; You will find everything manifested in the shunya, Everything arises out of shunya and Everything flourishes in the Shunya Brahman.
The philosophy sees Shunya as being full or whole (purna), and this view of Brahman is sometimes called the Purna Shunya (the full/complete void). The Panchasakhas project the deity Jagannatha as the embodiment of the Shunya Purusha. Achyutananda uses a classical (pre-Ramanuja) concept of Vaishnavism that uses both form, and formless aspects of god. This is seen in his statement from the Gurubhakti Gita :
dui je deṇāre pakṣī uḍikari jāi, dui je cakṣure sehi saṃsāre khelai. eka je na thile kaṇā dui gale anḍha, eṇukari nirguṇa saguṇa sehi bheda.
A bird can only fly with both wings. It can have a perfect vision with both the eyes. In the absence of one, it becomes one-eyed, and in the absence of both, it is totally blind. Thus like two eyes Nirguna [god perceived as formless]and Saguna [god perceived with form] are chained together.
The Panchasakhas were Vaishnavas by thought. But they differed from Chaitanya's path of devotion and preached Jnana-mishra bhakti or Devotion with mix of Wisdom. Chaitanya's path of devotion was known as Raganuga Bhakti Marga (brought to Odisha in 1509), which says all you need is love (devotion) to reach God.
The Panchasakhas believed that one needs a combination of love (bhakti) and wisdom (Jnana) to reach God. With our knowledge if we show our pure love (bhakti), we can definitely get the sunyatma (GOD). The Panchasakhas therefore promoted a Vaishnavism that involved study of scriptures, yoga, rituals, and devotion.
What Vedanta philosophy is followed in Utkaliya Vaishnava of Mahapurusha Achyutananda of Odisha?