Assalamu aleikum,
Ignorance at its base is a lack of knowledge. As defined in Webster's Dictionary:
Ignorance = : the state or fact of being ignorant : lack of knowledge, education, or awareness
Being in a state of ignorance is like being in the dark. It is only with the light of knowledge that a person can emerge. That is part of the reason why being in a state of continual learning and seeking of knowledge is so highly emphasized in Islam. And it is Allah alone who bestows whomsoever he wishes with knowledge, understanding, and right guidance.
Sometimes a person may find themselves in a state of ignorance through no real fault of their own. But if Allah brings the illumination of knowledge to us we must repent and be willing to change out of that previous state of ignorance in order to reap the benefits.
Umamah(ra) related that Rasulullah(saw) said, "Read the Quran, for it will come in the Day of Qiyamah as a torch to those that had read and followed it's teachings."
In the Qu'ran we find the following:
[16.119] Yet surely your Lord, with respect to those who do an evil in ignorance, then turn after that and make amends, most surely your Lord after that is Forgiving, Merciful.
[6.54] And when those who believe in Our communications come to you, say: Peace be on you, your Lord has ordained mercy on Himself, (so) that if any one of you does evil in ignorance, then turns after that and acts aright, then He is Forgiving, Merciful.
[48.26] When those who disbelieved harbored in their hearts (feelings of) disdain, the disdain of (the days of) ignorance, but Allah sent down His tranquillity on His Apostle and on the believers, and made them keep the word of guarding (against evil), and they were entitled to it and worthy of it; and Allah is Cognizant of all things.
And to those who have been entrusted with knowledge, an additional requirement ensues: you become obligated to not only act on the knowledge yourself, but you must also become dedicated to teaching others what you have learned.
Rasulullah(saw) said , "The best of charity is a Muslim who learns a knowledge and later teaches it to his Muslim brother."
Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) said, "Allah makes the way to Jannah easy for him who treads the path in search of knowledge .''
[Muslim].
Abu Musa (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) said, "The guidance and knowledge with which Allah has sent me are like abundant rain which fell on a land. A fertile part of it absorbed the water and brought forth profuse herbage and pasture; and solid ground patches which retained the water by which Allah has benefited people, who drank from it, irrigated their crops and sowed their seeds; and another sandy plane which could neither retain the water nor produce herbage. Such is the similitude of the person who becomes well-versed in the religion of Allah and receives benefit from the Message entrusted to me by Allah, so he himself has learned and taught it to others; such is also the similitude of the person who has stubbornly and ignorantly rejected Allah's Guidance with which I have been sent .''
[Al-Bukhari and Muslim]
Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) said, "The world, with all that it contains, is accursed except for the remembrance of Allah that which pleases Allah; and the religious scholars and seekers of knowledge .''
[At-Tirmidhi].
Ibn Mas`ud (May Allah be pleased with him) reported: The Prophet (PBUH) said, "Envy is permitted only in two cases: A man whom Allah gives wealth, and he disposes of it rightfully, and a man to whom Allah gives knowledge which he applies and teaches it .''
[Al-Bukhari and Muslim].
If we refuse to allow ourselves to be transformed by the introduction of truth, evidence and knowledge, the persisting in a state of ignorance is a terrible thing indeed. It is an arrogant, disobedience and constitutes disbelief. Consider the following:
[23.45] Then We sent Musa and his brother Haroun, with Our communications and a clear authority,
[23.46] To Firon and his chiefs, but they behaved haughtily and they were an insolent people.
[23.47] And they said: What! shall we believe in two mortals like ourselves while their people serve us?
[23.48] So they rejected them and became of those who were destroyed.
[23.49] And certainly We gave Musa the Book that they may follow a right direction.
[23.50] And We made the son of Marium and his mother a sign, and We gave them a shelter on a lofty ground having meadows and springs.
[23.51] O apostles! eat of the good things and do good; surely I know what you do.
[23.52] And surely this your religion is one religion and I am your Lord, therefore be careful (of your duty) to Me.
[23.53] But they cut off their religion among themselves into sects, each part rejoicing in that which is with them.
[23.54] Therefore leave them in their overwhelming ignorance till a [future] time
[23.55] Do they think that by what We aid them with of wealth and children,
[23.56] We are hastening to them of good things? Nay, they do not perceive.
[23.57] Surely they who from fear of their Lord are cautious,
[23.58] And those who believe in the communications of their Lord,
[23.59] And those who do not associate (aught) with their Lord,
[23.60] And those who give what they give.(in alms) while their hearts are full of fear that to their Lord they must return,
[23.61] These hasten to good things and they are foremost in (attaining) them.
[23.62] And We do not lay on any soul a burden except to the extent of its ability, and with Us is a book which speaks the truth, and they shall not be dealt with unjustly.
[23.63] Nay, their hearts are in overwhelming ignorance with respect to it and they have besides this other deeds which they do.
[23.64] Until when We overtake those who lead easy lives among them with punishment, lo! they cry for succor.
[23.65] Cry not for succor this day; surely you shall not be given help from Us.
[23.66] My communications were indeed recited to you, but you used to turn back on your heels,
[23.67] In arrogance; talking nonsense about the Quran, and left him like one telling fables by night.
[23.68] Is it then that they do not ponder over what is said, or is it that there has come to them that which did not come to their fathers of old?
[23.69] Or is it that they have not recognized their Apostle, so that they deny him?
[23.70] Or do they say: There is madness in him? Nay! he has brought them the truth, and most of them are averse from the truth.
[23.71] And should the truth follow their low desires, surely the heavens and the earth and all those who are therein would have perished. Nay! We have brought to them their reminder, but from their reminder they turn aside.
[23.72] Or is it that you ask them a recompense? But the recompense of your Lord is best, and He is the best of those who provide sustenance.
[23.73] And most surely you invite them to a right way.
[23.74] And most surely those who do not believe in the hereafter are deviating from the way.
[23.75] And if We show mercy to them and remove the distress they have, they would persist in their inordinacy, blindly wandering on.
[23.76] And already We overtook them with chastisement, but they were not submissive to their Lord, nor do they humble themselves.
[23.77] Until when We open upon them a door of severe chastisement, lo! they are in despair at it.
May Allah guide us in all truth, guide us to be among his most rightous servants, always increasing in knowledge and good practice of this beautiful religion of Islam he has blessed us with.
Wasalaam