Just trying to get a better understanding of all the different positions that Catholics take during the crisis. Sedevacante is simple enough to understand, but I need more information on Sedeprivationism and the Thesis. And information is greatly appreciated. Thanks.

They are synonyms. The thesis tries to solve a non-issue and contradicts cuм Ex Apostolatus in the process (it says the pope will have no partial power) among other things.

I've heard some say that some parts of that bull got abrogated.

For years, the preferred term on forums was sedeprivationism but it seems in recent years the preferred term has become "the thesis." I have no idea where the term "sedeprivationism" came from, and for all I know it's a term that non-thesis holders ascribed to thesis holders. I think "the thesis" (as a term) has become more popular due to Twitter (where I pretty much never see the term "sedeprivationism" used). And also, of course, because no one can pronounce "Cassiacicuм."

The basic purpose of the thesis (as described by its advocates) is to provide an explanation for the continuity of apostolic succession particularly in the area of jurisdiction.  Vatican I teaches that there will be shepherds and pastors continuously throughout all time. This is understood not to refer just to any Catholic man with Holy Orders, but specifically to those men who receive spiritual authority to govern and teach the faithful of Christ. Traditional Catholic clergy (with an exception or two here or there) were never incardinated into any diocese nor sent by any pope, and therefore simply do not have jurisdiction and therefore do not act with Apostolic authority.  

The thesis asserts that Novus Ordo heretics have a real material possession of the various offices they purport to hold, but lack formal possession due to not having the right intention to take up those offices (or at least that's how they view the papacy-- not sure if they view your typical episcopal see that way, but I assume they do).  Thesis holders assert that this material possession solves the problem of apostolicity and also gives us a "way forward" out of the crisis, whereby the conversion of any of these heretics would automatically result in their formal attainment to whatever offices they purport to hold.

I am not an adherent of the thesis, but I appreciate that thesis holders are aware of the theological problem of apostolicity and think it important to have an explanation of the crisis that solves that problem (the same cannot be said, for instance, of Fr. Cekada/Bishop Dolan [RIP] and their clergy).  I do think that if one of these antipopes were to convert to the faith that they would then be eligible to hold the papal office and, if their claim then was universally recognized, they would in fact be popes. I think history shows that sometimes you're only sure that that a man is pope, while not always being sure how he became pope.

But I don't really buy the whole "material possession" side of the thesis, or at least, I don't see material possession as something of any theological significance. 

It is more than mere human law that tells us heretics cannot hold office in the Church.

Never seen proof of this assertion.  If it was true, the +Bellarmine and everyone else wasted lots of time, energy and ink to debate the papal question long ago.

But I don't really buy the whole "material possession" side of the thesis, or at least, I don't see material possession as something of any theological significance.

I agree with you statement above.

For years, the preferred term on forums was sedeprivationism but it seems in recent years the preferred term has become "the thesis." I have no idea where the term "sedeprivationism" came from, and for all I know it's a term that non-thesis holders ascribed to thesis holders. I think "the thesis" (as a term) has become more popular due to Twitter (where I pretty much never see the term "sedeprivationism" used). And also, of course, because no one can pronounce "Cassiacicuм."

 to bolded.  So true. Not to mention spelling it correctly! 

Likewise, I rarely hear the term sedeplenism. I'm more likely to say (and hear) R&R or SSPX rather than "sedeplenist".

The thesis asserts that Novus Ordo heretics have a real material possession of the various offices they purport to hold, but lack formal possession due to not having the right intention to take up those offices (or at least that's how they view the papacy-- not sure if they view your typical episcopal see that way, but I assume they do).  Thesis holders assert that this material possession solves the problem of apostolicity and also gives us a "way forward" out of the crisis, whereby the conversion of any of these heretics would automatically result in their formal attainment to whatever offices they purport to hold.

But their ordination is doubtful..

What argument are you trying to make?

How can the NO clergy hold office (according to the thesis) if they aren't 'real' clergy?