All this was declared by Brahman himself. Applauded and practised by the foreinost of Rishis, and depending on Vedic knowledge it involves a consideration of what forms the real entity.
गुरुरुवाच ब्रह्मणोक्तमिदं सर्वमृषिप्रवरसेवितम्। वेदविद्यां समाश्रित्य तत्त्वभूतार्थभावनम्॥