Anybody who knows anything about Mage knows that arguments are easily had over what is Coincidental and what is Vulgar in any given mage game. The Mage supplements sometimes just confuse the issue. This place is to discuss that so we have some clear guidelines going forward. Having said that, Sphere magic is very freeform and loose, and I intend to give player creativity SOME leeway.

Right now, let us start off with the summoning/creating a business card in your coat pockets. A simple Matter/Prime or Matter/Correspondence Effect will give you the card. The question is: is this coincidental or vulgar? The very strict side says no, this clearly breaks accepted Consensual Reality and is thus vulgar without witnesses. The very loose side says yes, nobody saw it happen and many people have business cards in their pockets that nobody previously noticed, and is thus coincidental unless the Mage in question is very stupid about it.

Currently, I lean towards the second philosophy, mainly for player agency.

I would say that is the very definition of coincidental.  Also anything that could be played off as sleight of hand would fall into that category.

Thank you contributing Krazny :D.

Any conflicting and/or supplementary opinions out there?

And as far as what is coincidental/vulgar where, well I will be following something like the Reality Zone concept plus the whole 100 people of likeminded beliefs can make just about anything coincidental.

In the previous table top mage games I've played part of the casting is explaining how something is coincidental.  Part of the fun of mage (imo) is doing that.

Yes that makes sense to me as well PCO. Though in some cases I imagine the coincidental nature of a rote is obvious. Either way brief descriptions usually help. Also I am a big fan of describing how your Effect works, so I encourage it either way.

My only concern is when it comes to areas of expertise.  For instance, I have a medical background.  I can easily make an argument about how "coincidental" a stroke might be.  I have a friend that has a Masters in mathematics, so using numbers I've watched him make some weird arguments that few can follow.  So I do always become worried about a GM getting swamped with someone's expertise against their own.

There are ways to deal with such things.  For example, the character I am playing is going to have life 4 and a background in medicine, genetics, and biology.  If I decide to give someone a stroke or heart attack the GM can easily have me roll a science roll to see if I do it well enough the fool anyone who does an autopsy on the body.  If the roll fails then it is vulgar w/out witnesses.

Really I think it comes down to who is trying to mess with the rules and who is just trying to play the game.  I have found that Mage tends to discourage powergamers and min/maxers from playing, simply because you can't "escape" paradox.

Well I know a LITTLE bit about math theory, much more than actually doing it. I love learning about stuff like physics and astronomy, but I am not exactly well read on those subjects. All I can promise is to do the best I can. If players are unsure if something would be coincidental or not, please talk to me beforehand or the other players. My first reactions will be usually a sliding scale of Bullshit vs Player Agency.

And sometimes if you feel like you don't have the real life knowledge to make something coincidental but your character does, well rolling for it is a great way to handle it. Sometimes just simply having the dots will be fine.