Regarding Aristotelian Physics

T'was pointed out to me in the Errata that no longer do they include the bit about force being applied throughout the motion of an object. Presumably because of all the pre-1220 critiques of the idea, but that's just a guess on my part.

Given we're complete geeks, we're interested in knowing the in-universe reason for why MR stops natural Regoed items from impacting, since originally we explained that the force causing the motion (being magical) was negated on contact with MR. Our characters end up discussing theory at a disturbing frequency.

EDIT: Oh! Is there any recommendations on reading material that would be good for an introduction into the concepts of it? I'm interested in the real stuff for some history/philosophy work.

Well, Art & Academe (I received my author's copies yesterday. Yay!) has a discussion of this very issue, along with many more; with a particular focus on how this impacts on Hermetic Magic. HoH:S has a discussion on the lack of momentum in Mythic Europe and the consequences for spells. The two were written in concordance with one another.

Briefly, objects undergoing motion which is contrary to their nature need an initial mover and a motive power. For a thrown rock, for example, the initial mover is the thrower, and the motive power is provided by the air through which the rock is moving. This air, also affected by the rock's initial mover, pushes the rock.

Objects guided infallibly by magic have a magical initial mover and a magical motive power. It is the latter which is blocked by MR. Spells exist which only have a magical initial mover, and allow the motive power to be provided by the air. The motion of the targets of these spells is not resisted by MR, but they do need to be aimed.

The bibliography of A&A has some suggested sources.



The consequences of Aristotlean physics in Mythic Europe has some other features I've incorporated into my game. With no momentum or inertia, Strength has nothing to do with force in precipitate motion. Therefore,
Strength no longer adds to the damage of thrown or missile weapons in my saga.

Instead, Strength determines how far something will go. Add one fifth of the range increment for every point of Strength, or subtract if Strength is negative.

Thus a person with Str +5 and a longbow has range increments of 60 paces, instead of 30 paces. A person with Str -1 and a shortbow has range increments of 12 paces rather than 15. Naturally, minimum Strength still applies for these weapons.

Some would argue that the penalties apply more to accuracy than to distance, but our troupe has decided we can accept that for the mythic feel it gives.


For thrown weapons, I think this is actually more realistic. Like a spear, for the most part it is the weight of the spear that determines force of impact. Strength is needed to get it moving in the first place, and strength would definately affect range.

However, with the bow, I think you are sacrificing realism for philosophy. Great thinkers aside, the typical bowman knew that the more tension in the string, the bgreater the range and impact. I mean, this is just easilly observable. No medievial Welsh bowman is going to have any doubt that greater strength = greater draw tension = greater impact and range. Arched overhead, maybe just range, but a direct shot is obviously affected by the bow tension. Now, you can do like old school ad&d and say that the bow has to be built for that strength. Weaker people cannot use it and stronger people get no additional benefit whatsoever (not damage or range).

To quote the books, 'Some (magi/researchers) suspect this is a flaw in (Bonisagus'/Aristotles') theory.'

Medieval Scientist original research! Roll breakthrough!

And very cool, thanks. I should pick up Art and Acadame.

I would suggest

as a good resource for classical/medieval views on this issue, with further links.

Note that according to Aristotle, force must be applied throughout the motion of an object, or the object stops. However (to explain why arrows and other projectiles keep moving after being released) he posits that an object in motion creates a kind of vacuum (but not a complete void, see below) in the medium through which it moves, and this vacuum exerts the force that keeps the object moving. Thus, by pure Aristotelian physics, if you magically throw a stone, it is not stopped by magic resistance after the initial burst of force - the stone keeps moving by creating a (non-magical) vacuum in the air which propels it forward. It's a little bit like setting the surroundings of a target on fire magically - if they are combustible, after an initial burst of magical fire they burn non-magically and can bypass magic resistance.

This was clearly a rather unsatisfying part in Aristotle's physics, and was criticized very early. If you want magically thrown stuff to be stopped by magic resistance, you could say that the laws of the universe follow something close to the sixth century views of John Philoponus (which are themselves close to those of Hipparchus and Synesius): when you set an object in motion, you provide it with some sort of energy, or "impetus", which dissipates as it travels. This is somewhat more in line with today's basic view, though basically wrong. We have to wait for Avicenna, at the turn of the millennium, for the notion that motion stops only if hampered, so that in a void it would be unceasing.

Interestingly, Ithink*, though I might be totally wrong on this, that Aristotle's physics (and pretty much everything else with the exception of his Logic, which was translated by Boethius) were lost to the western world sometime after the fall of the Roman Empire, and were brought back only around the turn of the millennium through Arab translations preserved in the Muslim world. The western world rediscovered Aristotle's physics only through the commentaries of Avicenna, and the greek originals where still unknown until the 12th century, so I would consider "pure aristotelian" physics not necessarily in line with the mythic europe paradigm (by which what was generally believed correct in the early 13th century was indeed correct).

On the other hand, Aristotle's wacky notions might feel more exotic, and give a more mythic feel to the campaign. Some interesting tidbits are that, the less dense the medium through which an item travels, the faster it travels, and as the medium approaches void, the speed of the item approaches infinity. Great way to travel superfast by Muto Auram (or perhaps Perdo?)! One of the consequences is that, according to Aristotle's, complete void appears to be impossible, as matter would travel through it instantaneously, instantly filling it. (Hmm, what would be the consequences of this on Perdo?).

There's already a spell that destroys air. Possibly a spell effect to create a near-void corridor in your path.