I often work on aspects of magical applications to my own campaign milieu. Some people complain that magic isn't "mysterious" when it is treated like a science and so on, like magic is merely some kind of technology. Well, the old saying any technology can seem mysterious enough to seem like magic notwithstanding, I tend to think it is all in how it is presented in the campaign.
Certainly, if one wants all magic to seem like some great, wondrous enigmatic mystery of using mysterious, unknown forces and dealing with unfathomable entities or creatures, then it seems to me that an essential condition is to make wizards and magic-using classes extremely rare. That essentially means that in a practical sense, even player characters cannot choose to be wizards or clerics, or other magic-spell-using classes. They would have to roll randomly, with that chance being very remote and unusual as it is, and to also proceed to make the occurrence of any NPC spell-casters as similarly extremely rare and unusual.
Otherwise, if a more or less standard class availability model is embraced, then having spell-casters and their magic will be generally pervasive, and common. This, then, not only affects the player characters, but also the larger society within the campaign milieu.
That means that logically speaking, individuals and society in general will make extensive use of magic, and of spell-casting characters. That's just the way it is, and I find it to be somewhat difficult and problematic to see how some other result can be obtained if one is embracing the standard assumption.
That being said, then, what does magic embraced through all levels of society within the campaign milieu look like? How might the availability and subsequent knowledge, control, and predictability of magic affect the society at large?
Many of the often-cherished "Campaign Assumptions" embraced by the rulebooks and seen as the typical, default Dark Ages/Medieval European environment go right out the window if the same, contradictory magical assumptions from the books are subsequently embraced.
Consider the pervasive, powerful and dramatic effects that magic would reasonably have upon the typical medieval milieu:
Life and Death: Health, Longevity and Lifespan
The existence and development of Clerical and Druidic magic has a profound impact on all levels of society. Many campaigns play out in essence like they are "original bubbles"--that is, all of the magical assumptions and development are used in such a way as to seem like nothing has come before it. Just add water, voila!--the player characters enter into a world that remains remarkably static and seemingly unaware and unchanging of any knowledge of magic in previous generations--whether such campaign societies have been in existence for years--dozens of years, centuries, even thousands of years--the present age shows little evidence that anyone in the past actually thought about using and applying magic in different and sweeping ways that would forever change all of society.
All levels of society would benefit from Clerical and Druidic Magic. Wounds, illnesses, diseases, and ailments--even many aspects of aging--would be dramatically different, and would be greatly enhanced and improved in many, many ways. Such dramatic improvements in healing, health, and lifespan may at first only apply and be available to the wealthy and powerful--but eventually, such benefits would logically and inexorably filter down to nearly everyone. Perhaps only the very lowest echelons of society, and the otherwise classes of people deemed unworthy, worthless, or "untouchable" would suffer the main assumptions of a harsh, medieval existence.
Everyone else, however, would likely enjoy greatly enhanced lives of strength, vigor, health and happiness--as well as longer life spans, and thus more "time" in which to think, live, work, and accomplish things. These effects would also have a significant impact on societal views concerning "Age" and capability, health, expectations, as well as marriage patterns, career and work patterns, and the size of families. This in turn would have an enormous impact on the scale of population and demographics. The populations would be enormous, and constantly growing.
Imagine most such societies where the majority of the population does not have to fear most illnesses and diseases. They may live to easily 100 years or more, and much of that time would be in robust, vibrant health. The vast majority of common injuries, illnesses, and calamities that ordinary people endured during the Middle Ages would simply not exist. In many ways, such a society would more closely resemble the most affluent and modern societies of the present day, with some aspects being even more advanced and superior.
Labor and Manufacturing: Craftsmanship, Work and Technology
The existence and availability of LIGHT alone would dramatically affect society. Light alone. Think about what the impact of advanced availability of oil lamps and eventually electricity had on our own society; the availability of mass and personal light sources would dramatically change work patterns, manufacturing, and commerce. This, in turn, would affect ambition, wealth, and social mobility.
Businesses would operate with greatly extended hours--no longer hampered by restrictions of available sunlight. Such businesses would be available for work and commerce through the evening hours--and even 24-hour schedules of manufacturing and commerce would easily be attainable.
Magical applications would greatly improve the quality, durability, and performance of all kinds of tools, equipment, and machines, as well as manufacturing processes and techniques.
Agriculture, Animals and Food: Food, Drink, and Society
The existence and use of magic to improve soil quality, crop yields, durability, as well as the health and prosperity of all kinds of animals--from herd beasts to chickens, pigs, horses, and more--would expand the supply and quality of food to unprecedented levels. This dynamic in turn would also feed into the loop of extended health and lifespan, as well as population, as discussed earlier.
The existence of reliable food sources would also expand the development of various cuisines, as well as the storage, flavour, transport, and "shelf-life" of many kinds of food. This would increase the population's standard of living across the board, as well as increasing and enhancing commercial possibilities in kinds of businesses, eating patterns and habits, drinks, as well as transport, storage, supply, and marketing of foods and drinks in different ways to all levels of society, on a year-round basis, regardless of seasonal considerations or other degrees of natural availability.
Justice, Crime and Punishment: Laws, Courts, and Judgment
The society's justice system would be extensively impacted by magic. From the multitude of surveillance and detection spells, as well as spells dealing with binding, imprisonment, telepathy, and so on, would make determining guilt and innocence much more efficient and predictable. Various courts would understandably be developed dealing with how magic spells are used, when, where, on who, by whom, and in what circumstances. All of that would no doubt be quite complex--suffice to say, the development of a powerful Lawyer's Guild would be thoroughly present in any sizeable town or city. Such Barristers familiar with all manner of magical legal stipulations and codes would be essential, and pervasive. Execution may still remain a preferred aspect of justice--but also, viable, efficient and effective prisons enhanced by magic could also be developed for the purposes of extended imprisonment for those deemed worthy of life.
Wealth of Nations: Trade, Commerce and Society
Building on the previous commentary, a magical society would likely develop an enhanced and sophisticated economy--based either on coins or paper; either is serviceable and readily useful, though the availability and use of paper may otherwise be seen as an exotic possibility, or simply not realized. Still, either way, the economy will be advanced, complex, and sophisticated, with fully-functioning mints and coinage operations in place, and so on.
Banking concepts would likely be developed thoroughly, at least in some societies to a good degree. Insurance policies, investment policies and wealth management would develop as well. The creation, supply and maintenance of increased potentials of wealth and opportunities would soon encourage all of these kinds of developments, and lead to their implementation, at least to some degree.
Long range transportation, "Ice Wagons", freezer chambers, and so on within private homes, as well as businesses would not only enhance food production, supply and commerce, but also the development and trade of ever-burning campfires, cooking pots, cauldrons, ovens and stoves, would enhance food preparation and cuisine immeasurably, and in many significant and interesting ways.
The availability and variety of different kinds of restaurants, businesses, and so on would expand, as well as different kinds of construction materials, warehousing, storage, modes and speed of transportation, security of goods--not to mention improvements in sewers and waste disposal and management, development of "Greenhouses" and markets providing all manner of seasonal, fresh vegetables and fruits, as well as preserved meats, cheeses, milk, beers and other beverages, all of which would enhance not only every aspect of the market, but also expand numerous kinds of careers and professions, and enhanced wealth-creation opportunities and a richer, more diverse system of commerce.
Politics and War: Armies, Warfare and Espionage
Magic in warfare would change things significantly--with lots of magical effects acting as a kind of exotic artillery--while at the same time, many forms would likely remain the same, such as the need for infantry, cavalry, and specialized artillery units. After all, even with magic, there are still no combustible engines, armoured vehicles, flying machines, steel ships, submarines, machine-guns or other exotic, automatic weaponry or advanced explosive artillery or mass-produced firearms.
Certainly, the classical debates of magical offense and magical defenses can over time, act as counter-weights to each other. Regardless, however, warfare in a magical environment would still feature at least some modern-seeming, dynamic elements of especially hard-hitting and devastating forces of wizards, Special Forces, trained monsters, magically-enhanced cavalry forces, artillery, and so on. Such magically-enhanced military operations would be orders of magnitude above the typical pace of medieval warfare, and wars would have dynamic elements to them making range, speed, and concentrated power quite lethal, and serve as a constant aspect of battlefield awareness, tactics, and grand strategy.
Fashion and Art: Entertainment, Arts and Society
The influence and impact of the arts and entertainment is often overlooked in general--and often entirely so by assumptions presented in typical game books. However, the impact and influence of magically-enhanced entertainment upon all levels of society and culture in such a magical environment would be dramatic.
Think of the impact and influence of motion pictures--of movies and film upon society, and on how society shapes its values, assumptions, and expectations. Think of advertising, and marketing. These concepts, even though often essentially dependent upon modern aspects of technology, would certainly have aspects of them that would be developed and enhanced in a magical environment.
Nightclubs, dance clubs, bars, and so on with magically-enhanced music, constant and controllable lighting, various specialized mood and environment effects, and so on--as well as more formal theater productions and performances would have an interesting and provocative impact on all levels of society. The development and marketing of different kinds of sports and athletics--available both day and night--would likely be developed as forms of professional entertainment. Imagine the gladiatorial arenas, with magical lighting, special effects and so on, provided in great arenas and even magically recorded and made available on magical tapestries, scrolls, and so on to other, smaller communities and venues. Then imagine the commerce created by professional businesses and businessmen designed to provide, supply, and market such entertainment to the masses?
Imagine the effects of magic upon such institutional elements as libraries, bookstores, antique and curio shops, as well as zoos, animal parks, aquariums, and general parks available to the public--with both daytime and nighttime hours of operation, and all of the potential magical effects?
The entertainment value of shopping malls would also be present and significant--even without magic, in ancient times, for example, the Roman Emperor, Hadrian, established Hadrian's Market--now recognized as the world's first shopping mall. This wondrous place had some open-air elements, as well as enclosed businesses; it was seven stories tall, and covered hundreds and hundreds of acres, and could accommodate upwards of over 10,000 people at once, visiting, and going about business and hanging out. There were businesses and shops offering goods from all over the Roman Empire, as well as beautiful and vast bathhouses, restaurants, massage parlors, snack shops, smoking dens, philosophy clubs, lounges, and so on--all were available at Hadrian's Market. Hadrian's Market existed over 1800 years ago--and without magic.
Cultures in Transition: Society and Culture in a Magical Environment
Considering all of the commentary previously, the effects of magic on society would be profound, and sweeping. Of course, such a vision opens up whole new opportunities for stories and interesting, dynamic campaigns!