In Sri Ramakrishna's Jivan Charitra by M, Sri Ramakrishna has been quoted as saying:
If a thorn (Igonrance) has pierced your feet, then just by merely saying that "there is no thorn, there is no thorn", will the pain and the thorn be removed. No. To remove the thorn (Ignorance) , another thorn (Jnana) must be taken and with the help of another thorn, we should remove this thorn (Ignorance), and then throw away both the thorns (Igonrance and Jnana)
Similar explanation in advaita vedanta is found. Sri Adi Shankaracharya has said the following in his Prakaran Granth "Vivek Choodamani" (about how to remove the ignorance) as follows:
61. For one who has been bitten by the serpent of Ignorance, the only remedy is the knowledge of Brahman. Of what avail are the Vedas and (other) Scriptures, Mantras (sacred formulae) and medicines to such a one ?
62. A disease does not leave off if one simply utter the name of the medicine, without taking it; (similarly) without direct realisation one cannot be liberated by the mere utterance of the word Brahman.
63. Without causing the objective universe to vanish and without knowing the truth of the Self, how is one to achieve Liberation by the mere utterance of the word Brahman ? -- It would result merely in an effort of speech.
64. Without killing one’s enemies, and possessing oneself of the splendour of the entire surrounding region, one cannot claim to be an emperor by merely saying, ‘I am an emperor’.
65. As a treasure hidden underground requires (for its extraction) competent instruction, excavation, the removal of stones and other such things lying above it and (finally) grasping, but never comes out by being (merely) called out by name, so the transparent Truth of the self, which is hidden by Maya and its effects, is to be attained through the instructions of a knower of Brahman, followed by reflection, meditation and so forth, but not through perverted arguments.
66. Therefore the wise should, as in the case of disease and the like, personally strive by all the means in their power to be free from the bondage of repeated births and deaths.
67. The question that thou hast asked today is excellent, approved by those versed in the Scriptures, aphoristic, pregnant with meaning and fit to be known by the seekers after Liberation.
Source: Vivek Choodamani