According to MN 9 (below), as long as you still have fermentation or effluents, you would still have ignorance, and vice versa (also see this question). Ignorance is a very deeply ingrained and deeply lingering fetter. You know the Four Noble Truths, but when someone threatens your life, you may get scared. So, do you really know the Four Noble Truths in such a way that it dispelled your ignorance for good?
From the origination of fermentation comes the origination of
ignorance. From the cessation of fermentation comes the cessation of
From the origination of ignorance comes the origination of
fermentation. From the cessation of ignorance comes the cessation of
According to SN 35.153 (below), understanding by faith, by personal preference, by oral tradition, by reasoned reflection and by acceptance of a view after pondering it, is insufficient. It must be understood by "seeing it with wisdom". Only then does it obliterate ignorance permanently.
“There is a method of exposition by means of which a bhikkhu—apart
from faith … apart from acceptance of a view after pondering it—can
declare final knowledge thus: ‘Destroyed is birth … there is no more
for this state of being.’ And what is that method of exposition? Here,
bhikkhus, having seen a form with the eye (and same applies to sound
and ear), if there is lust, hatred, or delusion internally, a bhikkhu
understands: ‘There is lust, hatred, or delusion internally’; or, if
there is no lust, hatred, or delusion internally, he understands:
‘There is no lust, hatred, or delusion internally.’ Since this is so,
are these things to be understood by faith, or by personal preference,
or by oral tradition, or by reasoned reflection, or by acceptance of a
view after pondering it?”
“No, venerable sir.”
“Aren’t these things to be understood by seeing them with wisdom?”
“Yes, venerable sir.”
So, how does one "see it with wisdom"?
The answer comes in SN 22.98 (below), where Ven. Khemaka briefly describes the technique of Vipassana, as the method to be used to see with wisdom, in order to uproot the deep fetters of conceit and ignorance.
"In the same way, friends, even though a noble disciple has abandoned
the five lower fetters, he still has with regard to the five
clinging-aggregates a lingering residual 'I am' conceit, an 'I am'
desire, an 'I am' obsession. But at a later time he keeps focusing on
the phenomena of arising & passing away with regard to the five
clinging-aggregates: 'Such is form, such its origin, such its
disappearance. Such is feeling... Such is perception... Such are
fabrications... Such is consciousness, such its origin, such its
disappearance.' As he keeps focusing on the arising & passing away of
these five clinging-aggregates, the lingering residual 'I am' conceit,
'I am' desire, 'I am' obsession is fully obliterated."
The Buddha also confirms in SN 22.47 that when ignorance is fully overcome, the "I am" conceit would be fully obliterated:
“The five faculties remain right there, bhikkhus, but in regard to
them the instructed noble disciple abandons ignorance and arouses true
knowledge. With the fading away of ignorance and the arising of true
knowledge, ‘I am’ does not occur to him; ‘I am this’ does not occur to
him; ‘I will be’ and ‘I will not be,’ and ‘I will consist of form’ and
‘I will be formless,’ and ‘I will be percipient’ and ‘I will be
nonpercipient’ and ‘I will be neither percipient nor
nonpercipient’—these do not occur to him.”