Intelligence Makes the Wizard

Before we can begin looking at how magic would change society, we have to determine how much magic would be available to begin with. The prevalence of magic determines the extent of its impact. Yet how can we begin tackling this question?

As written by Pathfinder, the only limitation on how powerful a wizard can become is:

To learn, prepare, or cast a spell, the wizard must have an Intelligence score equal to at least 10 + the spell level. 

Spell levels range from 1 to 9, so to be able to cast you would need the opportunity to study magic, and an INT of at least 11.

What's the bell curve on intelligence in society? Oh, here's a handy graphic:

Let's apply those percentages to 13th century France. Demographics show that the population was about 13 million by the end of the century. Let's do some very rough sorting. Mortality rates were very high in the medieval world. I think we can say that half the population was below the age of 18. That leaves 6.5 million adults. Since only men could receive an education, we can further narrow that number down to 3.25 million adult men. Let's further say that 2/3rds of these men are serfs or simply the working poor, and we're down to about 1 million potential mages who make up the nobility, the clergy, and the wealthier merchants and traders of the upper middle class.

According to the bell chart, half of those men would be of below average intelligence, so we're working with 500,000. 68% would have an INT of 10 - 11.

Our potential wizards would have to be drawn therefor from a pool of 160,000 men. 70,000 of them would have INT 12 - 13. 10,000 men would have INT 14 - 15. 650 men would have INT 16+.

Our final results:

INT 12 - 13: 70,000 men
INT 14 - 15: 10,000 men
INT 16 - 18: 650 men

These numbers would probably be a little larger as there would be 8,450 INT 16+ individuals in the society as a whole, and that level of intelligence would be noticed and groomed for magic, regardless of gender or class. But overall, we can work with those inexact numbers to get a sense of the ratio of potential wizards to regular people in 13th century France. Would each of these men become a wizard? Hardly. But with magic being so lucrative and powerful, the drive would be there for all men of intelligence to at least learn the rudiments, and the more intelligent the man, the more likely he would be to devote his life to earning power.

What this means is that casters capable of magic up to 3rd level spells would be relatively common, appearing in all cities like most traders do. Casters capable of magics of up to the 5th level would be much rarer, but still readily available to those willing to pay for their services. Wizards capable of casting spells up to the 9th level would be very rare, probably known by name, and reside in positions of power across the land. Their services would only be available to the truly wealthy or those in power.

Of final note: zero level cantrips would be common, as any of the 500,000 INT 10+ men could learn them with a little effort and dedication, becoming in effect a 1st level wizard with no potential to cast 1st level spells. 

New Project

Brandon Sanderson's Third Law of Magic is: expand what you already have before you add something new. He explains:

Often, the best storytelling happens when a thoughtful writer changes one or two things about what we know, then extrapolates purposefully through all of the ramifications of that change. A brilliant magic system for a book is less often one with a thousand different powers and abilities—and is more often a magic system with relatively few powers that the author has considered in depth.

In epic fantasy books, it’s not the number of powers that creates immersive and memorable worldbuilding—it’s not even the powers themselves. It’s how well they are ingrained into the society, culture, ecology, economics, and everyday lives of the people in the stories.

My new project involves a slow examination of how the magic spells available to wizards would change the world they live in. Too often D&D settings are merely a simplified medieval setting, with magic limited to a handful of wizards in their towers and mystical weapons and wondrous objects. Careful thought can extrapolate how even simple spells would change the way this world works, much less more powerful spells such as teleport and magic jar.

I'm going to start with a society based on 13th century France, and then slowly introduce one spell at a time, starting with cantrips and working my way up. As I go, I'll continuously modify my theoretical society, extrapolation and changing it to reflect the cumulative consequence of the spells available to wizards.

Why 13th level France? At that time, France was the largest and most powerful country in Europe. Unlike the disastrous 14th century, the 13th century was a time of growth, invention, and cultural flowering. With a firmly established king, an entrenched system of powerful nobles, a wealthy and extensive clergy along with its downtrodden base of peasants and serfs, France from that time serves as an ideal model to what most DM's inadvertently think of when they imagine a medieval setting.

I'm going to start with some basic questions, and then move to the spells. How prevalent would magic be? Whom would learn magic? What would their limitations be, and what role would these mages play in society?