Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 34

Sanskrit:

आत्मा परिज्ञानमयो विवादोह्यस्तीति नास्तीति भिदार्थनिष्ठ: ।व्यर्थोऽपि नैवोपरमेत पुंसांमत्त: परावृत्तधियां स्वलोकात् ॥ ३४ ॥

ITRANS:

ātmāparijñāna-mayo vivādohy astīti nāstīti bhidārtha-niṣṭhaḥvyartho ’pi naivoparameta puṁsāṁmattaḥ parāvṛtta-dhiyāṁ sva-lokāt

Translation:

The speculative argument of philosophers — “This world is real,” “No, it is not real” — is based upon incomplete knowledge of the Supreme Soul and is simply aimed at understanding material dualities. Although such argument is useless, persons who have turned their attention away from Me, their own true Self, are unable to give it up.

Purport:

If one doubts the existence of the Supreme Personality of Godhead, one will inevitably doubt the reality of the Lord’s creation. Thus, without understanding Lord Kṛṣṇa, mere argument and debate over the reality and nonreality of the material world are useless. The material world is real specifically because it emanates from the supreme reality, Lord Kṛṣṇa. Without understanding the reality of Lord Kṛṣṇa one can never definitely ascertain the reality of His creation; one will always wonder if he is actually seeing something or merely thinking that he is seeing it. This kind of speculation can never be resolved without taking shelter of the Supreme Lord and is therefore useless. The devotees of the Lord are not inclined to such argument, because they are factually advancing in spiritual enlightenment and are fully satisfied with their progressively more beautiful experience of Kṛṣṇa consciousness.