Biblical Prohibition of Breaking Shabbos/Shabbat because one didn't learn the laws

Question

Somebody does not think that something is breaking Shabbos but suspects it may be an issue, yet they don't want to delve into the law because they don't want to stop doing what they are doing and they rely on their logical assumption that it is okay (e.g. melachot not mentioned in the Torah or Talmud; not realizing the science behind the action).

Is this person fully liable under Biblical law (to bring a korban as shogeg, meizid liability, etc.) when they logically believe that it is allowed (even though they are not 100% sure that is the proper law)? If yes, then does it make a difference if a minority (halachikly valid) opinion supports them?

(I would think that there is liability and it is a shogeg because it is not a deliberate violation. However, if they know the science behind it, then they are consciously doing the melacha action; therefore, if they suspect that it is a problem, they may be considered a meizid. On the other hand, the suspicion may need to be an obvious one--like where everyone knows it is a halachik prohibition--to even consider this person a meizid.

The other factor is when a minority opinion supports this person's incorrect view. One can argue that even though the view is not normative halacha, because there is no Sanhedrin there is no liability all together, even if the person is a meizid (there may be other issues in heaven for such an individual, but not connected to chillul Shabbat liabilities). However, one can argue that the future Sanhedrin can retroactively cause liability when they vote on what the law follows. This aspect of the question is a whole other lengthy topic.).

Answer 1

Ralbag writes as follows in his commentary to Parshat Nitzavim:

התועלת השני הוא להודיע שמי שירצה להסיר מעליו עול התורה בשלא יכוון לדעת עניניה כדי שיהיה שוגג בכל מה שיעבור עליו מדברי התורה ולא יענש על זה הנה לא תועילוהו המחשבה הנפסדת הזאת [להצילו] מן העונש אבל יענש יותר ומחה ה' את שמו מתחת השמים כאמרו כי אז יעשן אף ה' וקנאתו באיש ההוא

The second lesson is to make known that one who wants to remove the yoke of Torah from himself by not directing [himself] to know its contents, in order to be [classified as an] unintentional [violator] in everything that he violates of the words of the Torah and [therefore] not get punished for this, will not be helped by this disgraceful thought to save him from punishment. Rather, he will be punished [even] more, and God will erase his name from under the heavens as said "for then the anger and jealousy of God will smoke against that man".

Answer 2

This is definitely an instance of "shogeg", i.e. they are violating through "carelessness" for which they have a level of liability.

The 7th chapter of Mishnah Shabbos and the G'morah states what liability they will have in "zeh ha'klal".

If they perform the same category of melacha over and again, even of several shabboses, they will be liable for 1 korban for that category of melacha.

So if they are shogeg (careless) over 4 different categories (of the 39) they will need to bring 4 chatot once they find out.

Of course once they find out that this action is prohibited they would have to then "forget" before the next Shabbat occurs.

If they were taught the halacha but forgot it, this opens up a new period of forgetfulness. (G'mara goes into this issue). So if they, say, did something that constitutes building, then remembered the halacha, then forgot again and did again something that constitutes building, that is 2 korbanot because there were 2 separate periods even though it was one category.

Of course nowadays we do not have korbanot, but it is useful to learn chapter 7 of Shabbat for the sake of learning.

The Gemara mentions someone how knows there is a concept of Shabbat and that Melacha is prohibited on it, but did not take the effort to find out more when they could have done. That is really the case you are discussing. There is also mentioned the person who did not know anything about Shabbat and it says they require one korban for everything, although I think the Gemara questions how such a person can be liable at all. They also discuss the person who is liable for 39 chatot, who only knew the law of Techumim.

Of course, to be liable for korban chatat, it has to be a bibical prohibition, not a Rabbinic one.

With regards the minority opinion, it could even be that both agree that something is forbidden but they disagree whether the prohibition is biblical or Rabbinical, but I believe that sometimes the majority opinion even determines what the Biblical halacha is. I can't therefore give specifics to that particular use case but hopefully by the time the Moshiach comes and builds the Temple, you'll be able to get the shayla answered as to how many korbanot you (or whoever) owes.