(Bhagavan Sri Krishna)
"Unless Kṛṣṇa gives you protection, there is no protection. This is stated in the Śrīmad-Bhāgavatam: bālasya neha śaraṇaṁ pitarau nṛsiṁha (SB 7.9.19). When Prahlāda Mahārāja, offering prayer to Kṛṣṇa, Nṛsiṁha-deva, he said, 'My dear Lord, bālasya, for the children, it is not to be thought that because one child has got father and mother, he has got full protection. No. That is not.' If Kṛṣṇa does not give protection to a child, in spite of having thousands of father and mother, he'll not be protected. This is the fact.
Similarly he says, nārtasya cāgadam udanvati majjato nauḥ (SB 7.9.19). It is not that good physician or good medicine can give one protection. No. Suppose one is suffering from some disease and one is very rich man. He engages first-class physician; first-class medicine is being... Does it mean that his life is guaranteed? No. If Kṛṣṇa does not give him protection, despite all supply of good medical treatment and medicine, he'll die. This is a fact. Similarly, if you have got good, nice boat, it is not guarantee that you'll not drown in the ocean. No. At any moment, if Kṛṣṇa does not give you protection... This is our position.
So we may have invented so many counteract..., counteraction for our protection. That is scientific advancement, struggle for existence. Nature is offering difficulties, and the human beings, so-called scientists, they are trying to invent something to check this difficulty. This is called struggle for existence. But it is not possible. Unless Kṛṣṇa gives you protection, your invention has no use."
(Srila Prabhupada Lecture, Los Angeles, April 29, 1973)