SB 7.15.58

ābādhito ’pi hy ābhāso
 yathā vastutayā smṛtaḥ
durghaṭatvād aindriyakaṁ
 tadvad artha-vikalpitam
Synonyms: 
ābādhitaḥ — rejected; api — although; hi — certainly; ābhāsaḥ — a reflection; yathā — as; vastutayā — a form of reality; smṛtaḥ — accepted; durghaṭatvāt — because of being very difficult to prove the reality; aindriyakam — knowledge derived from the senses; tadvat — similarly; artha — reality; vikalpitam — speculated or doubtful.
Translation: 
Although one may consider the reflection of the sun from a mirror to be false, it has its factual existence. Accordingly, to prove by speculative knowledge that there is no reality would be extremely difficult.
Purport: 

The impersonalists try to prove that the varieties in the vision of the empiric philosopher are false. The impersonalist philosophy, vivarta-vāda, generally cites the acceptance of a rope to be a snake as an example of this fact. According to this example, the varieties within our vision are false, just as a rope seen to be a snake is false. The Vaiṣṇavas say, however, that although the idea that the rope is a snake is false, the snake is not false; one has experience of a snake in reality, and therefore he knows that although the representation of the rope as a snake is false or illusory, there is a snake in reality. Similarly, this world, which is full of varieties, is not false; it is a reflection of the reality in the Vaikuṇṭha world, the spiritual world.

The reflection of the sun from a mirror is nothing but light within darkness. Thus although it is not exactly sunlight, without the sunlight the reflection would be impossible. Similarly, the varieties of this world would be impossible unless there were a real prototype in the spiritual world. The Māyāvādī philosopher cannot understand this, but a real philosopher must be convinced that light is not possible at all without a background of sunlight. Thus the jugglery of words used by the Māyāvādī philosopher to prove that this material world is false may amaze inexperienced children, but a man with full knowledge knows perfectly well that there cannot be any existence without Kṛṣṇa. Therefore a Vaiṣṇava insists on the platform of somehow or other accepting Kṛṣṇa (tasmāt kenāpy upāyena manaḥ kṛṣṇe niveśayet).

When we raise our unmixed faith to the lotus feet of Kṛṣṇa, everything is revealed. Kṛṣṇa also says in Bhagavad-gītā (7.1):

mayy āsakta-manāḥ pārtha
 yogaṁ yuñjan mad-āśrayaḥ
asaṁśayaṁ samagraṁ māṁ
 yathā jñāsyasi tac chṛṇu

“Now hear, O son of Pṛthā [Arjuna], how by practicing yoga in full consciousness of Me, with mind attached to Me, you can know Me in full, free from doubt.” Simply by raising one’s staunch faith in Kṛṣṇa and His instructions, one can understand reality without a doubt (asaṁśayaṁ samagraṁ mām). One can understand how Kṛṣṇa’s material and spiritual energies are working and how He is present everywhere although everything is not Him. This philosophy of acintya-bhedābheda, inconceivable oneness and difference, is the perfect philosophy enunciated by the Vaiṣṇavas. Everything is an emanation from Kṛṣṇa, but it is not that everything must therefore be worshiped. Speculative knowledge cannot give us reality as it is, but will continue to be nefariously imperfect. So-called scientists try to prove that there is no God and that everything is happening because of the laws of nature, but this is imperfect knowledge because nothing can work unless directed by the Supreme Personality of Godhead. This is explained in Bhagavad-gītā (9.10) by the Lord Himself:

mayādhyakṣeṇa prakṛtiḥ
 sūyate sacarācaram
hetunānena kaunteya
 jagad viparivartate

“This material nature is working under My direction, O son of Kuntī, and it is producing all moving and unmoving beings. By its rule this manifestation is created and annihilated again and again.” In this regard, Śrīla Madhvācārya gives this note: durghaṭatvād arthatvena parameśvareṇaiva kalpitam. The background of everything is the Supreme Personality of Godhead, Vāsudeva. Vāsudevaḥ sarvam iti sa mahātmā sudurlabhaḥ. This can be understood by a mahātmā who is perfect in knowledge. Such a mahātmā is rarely seen.