Is argument from ignorance always fallacious?

Thanks for your answer Kaiden! Reading your answer and comparing it with the definition of argument from ignorance I noticed that the definition is misleading and ambiguous to me.

I find misleading the part that says, "The assumption of a conclusion or fact"

• If it is a conclusion, that means there is some reasoning behind it (as you say in your answer some Modus Ponens implicit argument)
• If it is a fact, then it's something that has happened, and can't be questioned.

I also find ambiguous the phrase, "based primarily on lack of evidence to the contrary"
What does "primarily" mean? Why not just say "because of lack of evidence to the contrary".
Because if I understood your answer correctly, if there is any other reasoning (even implicit), then it's not Argument from Ignorance.

A less ambiguous/misleading definition for me would be:
"Assuming a claim is true because of/based on lack of evidence to the contrary"

Do you agree? 

[To Kostas Oikonomou]

You’re welcome! I don’t keep internet at my home, so thank you for your patience as I schedule traveling to internet hotspots to see your comments, then consider and send replies. I understand where your concerns are coming from, but some key points will mitigate them and help us see why the definition offered by Dr. Bennett is good enough.

Your unspoken thought seems to be that a statement reached in the course of committing the argument from ignorance fallacy is not a conclusion because no reasoning stands behind it, and the committing of the fallacy is what amounts to the absence of any reasoning. 

That understanding of reasoning is not appropriate for this context, however. For the purposes of logic—separating good from bad arguments—a reason is a statement someone gives in attempting to persuade you rationally to believe a further statement. A reason is a statement in the role of a premise . The statement to be persuaded of, which the premises are intended to justify through an inference, is in the role of the conclusion. Reasoning, for the purposes of logic, is the movement from the premises to the conclusion, judging that the conclusion is true on account that the premises are. All arguments from ignorance involve reasons and reasoning in the senses of a statement in the role of a premise and a judgement of truth moving from it to the conclusion. 

It is plain that the prior understanding of reason was inappropriate, you see, because this logical fallacy cannot occur where there is no conclusion. Where there is no conclusion, there is no argument to contain the logical fallacy. 

On to facts. I see why you characterize facts in that way. However, just because something is a fact, does not mean that your attempt to rationally persuade a person that it is a fact is a good attempt. Committing the argument from ignorance is about the badness of an attempted rational persuasion (an argument), regardless of whether the attempt so happens to have as its aim your acceptance of a factual statement.

Dr. Bennett’s definition is not so misleading with an understanding of “conclusion” proper to this context, and with a better understanding of why the factuality of a conclusory statement is a separate issue from the integrity of the inference to it. Let’s talk about ambiguity, now. 

As for answering any ambiguity in the language, that is Dr. Bennett’s task. Though he might take an explanatory path that involves showing how the definitions that “primarily” is ambiguous between are all workable anyways, and the word may at worse be superfluous, and at best acknowledges that an argument committing the fallacy might have other, less serious complexities going on. But we’ll see what he does. 

Because if I understood your answer correctly, if there is any other reasoning (even implicit), then it's not Argument from Ignorance.

Thank you for taking time to read and think on my answer. However, this is not the understanding to come away with. The point I made is that if you assume, in the course of arguing that an unproven statement is false, that proof would be had if the statement were not false, then you are not arguing from ignorance. It is specifically this sort of reasoning that I highlighted.

A less ambiguous/misleading definition for me would be: "Assuming a claim is true because of/based on lack of evidence to the contrary" Do you agree?

Well, there is nothing so crucially problematic with that definition that it’s worth my steam, or probably any other philosopher’s, to criticize it in a casual conversation. Your proposal shows that you grasp the idea. So, if it is less misleading and ambiguous for you, then hold to it. But since you are going out of your way to ask me, I will make a few points, then close. “Conclusion” is more precise than “claim” because the statement claimed is being argued for and the fallacy occurs in the course of arriving at the claim qua conclusion.  “Assume” is an inappropriate word because a conclusion is not an assumption, for an assumption is a statement made without a premise aiming towards it, whereas the claim in question has standing for it a premise. 

Thirdly, I won’t buy the phrase “lack of evidence” because you can commit the fallacy even if you concede that the statement you regard as false (or true) has at least some amount of evidence going for it. I prefer, for that reason, the phrase “lack of proof” or “because it has not been proven.” The logician under whom I learned this fallacy also defined the fallacy in terms of proof/disproof and died without leaving an explanation of why he did (and my seance over the weekend bore no fruit.) The explanation I have just given may have been why. 

Well, thank you for you thoughtfulness and courtesy, and for waiting on a reply for a few days. 

No worries man, it goes without saying that you will write back when and if you have spare time and the means (i.e internet) to do that. Thank you for your extensive reply, although I can't say I managed to follow your thought all the way.