Magic and technology are opposites. Magic bends physical law to the will of the mage. Technology depends on physical law. And, in the fantasy world of Arcanum the use of technology reinforces physical law, countering the effect of magic.

The spell Stone Missile works by summoning a small rock out of thin air (physically impossible!), and then accelerating the rock to high speed along a finely controlled trajectory, merely by force of will (also physically impossible). In contrast, a gun takes advantage of several physical laws to achieve the same ends.

In Arcanum each use of magic weakens physical law, and each use of technology reinforces it. This dichotomy is directly built into the gameplay. To model this in a fun, and not overly complex manner, the state of physical law is tied to the people who change it. A practiced mage weakens the law, and that weakness of physical law becomes a part of the mage, following him wherever he goes. A studied technologist reinforces the law, and that strength of physical law becomes a part of the technologist, traveling with him.

The game examines a character's skills and derives from them a quantitative aptitude towards magic or technology. A character who knows several spells but only one technological skill will have a significant magical aptitude. A character who has mastered several technological skills but only one spell will have a high technological aptitude.

This stat is used to modify the effectiveness of every spell and every technological skill as they are used by that character. A character with an aptitude for magic receives a bonus when casting spells, and a penalty when using a technological skill. As you can guess by now, the reverse is true for technology.

It is also possible for a character to study equal amounts of magic and technology. That character's magical and technological aptitude will hover near zero. Spells and technological skills will both work normally for the balanced character, without penalties or bonuses.

f you shoot a gun at a skilled mage, the bullet will have difficulty maintaining a steady trajectory, and may miss on account of this. The mage weakens the physical laws that the bullet uses to stay on target, such as the stabilization imparted by spin. The spell Stone Missile will have a similar problem when used against a master technologist. The technologist reinforces physical law, making it harder for the Stone Missile to stay on target, or to impact with the usual force.

When one character uses a skill on another character, both characters' aptitudes are taken into account. The acting character may receive a bonus or penalty from his own aptitude. The aptitude of the target can contribute a penalty, but not a bonus.

When a spell is cast, the technological aptitude of the target is subtracted from the magical aptitude of the caster. If the result is positive, a corresponding bonus is applied to the spell, representing the superior magical aptitude of the caster. If the result is zero, the match is even, and the spell activates normally, without a bonus or penalty. If the result is negative, a penalty is applied to the spell, representing the superior technological aptitude of the target.

Sometimes the caster might have a technological aptitude instead of a magical aptitude -- perhaps this character is an engineer who has learned just one or two spells for when they're handy. In this case the technological aptitude of the caster will be treated as a negative magical aptitude to begin with. If the target also has a technological aptitude, this will be subtracted from the initial negative number to make for an even larger penalty.

The same pattern holds for the use of technological skills, just with a switch of aptitudes. This rule also affects the use of beneficial skills, such as healing.