The idea that a person would do something which they regard as “wrong” or to be “evil” is typified in the experience of Abraham (Gen. 22: 2) and Nephi (1 Ne. 4: 10.). This is what the Lecture is talking about when it says:
The post I put up with an excerpt from Lecture 6 a bit ago was deliberately chosen as a foundation for what was put up a few days ago. That Lecture included the fact that you “know” not merely “believe” that what you are doing is in conformity with God’s will. A person obtains “actual knowledge” that they are acting in conformity with God’s will.
Kisi asked a question regarding the idea of being asked to do something you regard as “wrong” or perhaps even “evil,” and how can a person avoid deception with such an idea. The answer lies within the doctrine taught in Lecture 6. You simply cannot proceed without knowing. You cannot know without following the correct course. You must make an acceptable sacrifice to obtain the knowledge. Without making that sacrifice you cannot obtain that knowledge. However, once you have possession of the actual knowledge, then it is not a matter of conjecture, or speculation, or desire, or “hope” as the world uses that term. Rather it is an act in utter righteousness, in strict conformity with the will of God, whose will is known to the person because they have proceeded correctly in obtaining this knowledge.
To gain that knowledge a person keeps the commandments, pays their tithes, does everything they are asked to do to follow the will of God as understood by them. Such a person will be “firm in their minds” and not weak minded or given to flights of fancy. (Moroni 7: 30.) They will have been qualified by the things which they have done in following God to possess this kind of knowledge.
“a religion that does not require the sacrifice of all things, never has power sufficient to produce the faith necessary unto life and salvation; for from the first existence of man, the faith necessary unto the enjoyment of life and salvation never could be obtained without the sacrifice of all earthly things; it was through this sacrifice, and this only, that God has ordained that men should enjoy eternal life; and it is through the medium of the sacrifice of all earthly things, that men do actually know that they are doing the things that are well pleasing in the sight of God.”
Now I do not expect anyone to be asked to sacrifice their only child. Nor to be told to kill someone and take their possession. What I expect is that in the context of the life someone has lived or is living, they will be asked to do or not do something which is so specific to them that they alone will understand why it is a sacrifice to them. If asked of another, it may be completely insignificant. But when asked of them, it will be exactly what the person will struggle to lay upon the Lord’s altar. Hence the term “sacrifice” with its partial meaning of parting with something involving great value to them. However, it is not possible to rule anything in or out – the Lord alone will know you and what is required for you to obtain this faith.
The terms for obtaining this kind of faith are the same for every man or woman who has ever lived. Without making the sacrifice it is not possible to obtain the faith.