In D&D, when a cleric casts a spell, what really happens? The rules are pretty clear on the mechanics of
bless or
cure light wounds but what about the story? Are the deities aloof, or do they intervene in the world? D&D has taken a number of positions on this issue.
The earliest position is that clerical spells are similar to wizard spells, but a cleric prays for each spell on a regular basis. His deity grants that spell to him, and when he wants to cast it again, he must pray again the next day. Acting against the tenets of the religion may interfere with a cleric's spellcasting powers at the DM's discretion. This is the basic position of the earliest editions through early second edition.
One alternative that is generally presented in early D&D is that a cleric may worship a philosophy or force (i.e. goodness) instead of a deity. Who 'grants' the cleric spells isn't really defined in this alternative system. This system, however, seems to be targeted at groups who want to portray clerics but don't want to get into the details of developing and portraying a fictional religion.
Over the course of second edition, a few alternative perspectives arose. Al-Qadim developed a religion of enlightened gods who represented ideals (bravery, adventure, wisdom, etc.) and let their churches and priests be differentiated based on cultural aspects (the Pantheonists only admitted 5 enlightened gods, while the Temple of 10,000 Gods admitted them all). The Dark Sun setting, instead, split clerics into elemental worshippers and those who gained their power by serving neigh-omnipotent sorcerer-kings. Elemental priests got their spells from a nebulous somewhere, whereas the templars clearly got their spells from an active agent in the world.
Third edition presents clerics much as before, though they have ways of channeling their deity's power without spells. Third edition clerics are still at the mercy of the DM if they act against the wishes of their deities.
Finally, fourth edition frees clerics from the tyranny of the DM by making the gods aloof in the world. Clerical magic (same for Paladins and Avengers, though not Invokers or Runepriests) is granted by an ordination ceremony, which allows the Cleric to channel the powers of the astral sea. They technically don't need to worship the deity for a second after that ceremony, and can continue casting spells all day long. This also differentiates divine magic from arcane magic, as divine magic arises from the astral sea. One strange effect here, however, is that all clerics draw upon the same pool of powers, so clerics of evil deities, sea deities, or darkness are also liable to be slaying their foes with holy radiance. Divorcing clerical magic from worship of the deities may seem odd, but it also means that a cleric cannot lose spellcasting powers if he does something against his faith. Given the edition's power system, this is important as any character who loses access to his powers is crippled.
Two of the more curious systems arose in the second edition
Spells and Magic book. While tied to a complex spell-point system, divine magic was presented with two interesting options that DMs could use. The first is ritual prayer, and the second is conditional magic.
In the ritual prayer system, the cleric's deity isn't invested in the cleric's prior actions, but just the act of completing the ritual properly:
"In this system, the deity or power is concerned more with the priest’s show of devotion and observance of the proper form, and considers the priest’s actual situation to be irrelevant—after all, martyrs are made every day."
Here, we get a solid system for clerical magic in which the deities are aloof and seem to take no part in the affairs of the world. Clerical magic is ritualized, and rushing the ritual is likely to reduce the power of the spell. Conversely, ritual prayer made by a ritually pure priest (observant, not necessarily pious) with the proper offerings ad the proper place and conducted with care can produce spectacular effects. With the right casting conditions, even previously expended spells can be cast again! Its all about the motions, however. In this way, the ritual prayer system can be seen as a precursor to the 4e system. Moreover, it links the cosmology (aloof deities) to the magic of clerics.
These aloof deities make divine magic feel much more like the magic in the D20 Conan game and Conan universe in general. While independent sorcerers exist, many are trained in the priesthoods of these aloof and alien deities. Whether or not the god even exists is not important: it is the ritual training of the priests that give them sorcerous abilities.
The inverse system is also presented as Conditional Magic. In this system, the gods carefully answer each prayer based not necessarily on the urgency of the petitioner but on the probability to influence the world in a way the deity prefers. When a cleric casts a spell, you tally up the total of positive and negative conditions. If it is skewed heavily positive (casting a spell to smite the deity's enemies in a holy place, etc.) the spell is cast at a higher caster level or reduced in cost. If it is skewed negatively, the spell is more costly or weaker.
The conditional magic system presents interventionist deities, and their tools are their clerics. The mechanics explicitly reward clerics for advancing their deity's agenda and penalties for working against it. This codifies some of the DM fiat where by the DM may simply neuter a cleric by taking away all his spells.
The idea of interventionist deities can be clearly seen in the Dark Sun novel
Rise and Fall of a Dragon King:
"O Mighty Hamanu! Lion-King, Lord, and
Master, hear me!"A distant
voice echoed in Hamanu's mind. The totality of his awareness raced backward,
along a silver thread of consciousness through the Unseen netherworld, to the
source.
"Armor! I crave invincible armor and
earthquake!
"The Gray was
charged with acid needles, and Hamanu's vision, when he opened his sulphur eyes
above the desperate templar, was streaked with lurid colors. There was powerful
magic—someone else's powerful magic—in the vicinity.
"O Mighty Hamanu! Hammer of the World!
Grant me invincible armor and earthquake!
"Squinting
through the magic, Hamanu made out chaos and bloodshed: a full cohort of his
own templars outnumbered by ragtag brigands. Or, not brigands. Another moment's
study discerned a well-armed, well-drilled force disguised for brigandage. In
the midst of the Urikites' impending defeat, a militant, a human man with tears
of panic streaming down his face, raised his bronze medallion and entreated the
Lion-King for the third time:
"O Mighty Lion, grant me invincible
armor and earthquake, lest I die!
"A wise invocation—in its way. An
earthquake, if Hamanu empowered the spell to create one, would swallow
everything on the battlefield, friend and foe alike, except for the invincibly
armored militant. Though sacrifice was necessary in battle, the Lion-King of
Urik was not in the habit of rewarding militants who'd save themselves and doom
the lesser ranks and mercenaries they led. He'd have considered granting the
earthquake while withholding the invincible armor—and savored the militant's
death—if the netherworld turbulence wouldn't have negated any spell he granted.
If you want to portray deities like that, the basic D&D cleric system of divine magic doesn't quite cut it, though using the conditional magic system definitely helps.
These two systems nicely define and differentiate two distinct types of deities: aloof vs interventionist. It is even somewhat easy to imagine distinct classes using different systems, such as a Dark Sun game where the elemental clerics use ritual prayer while templars (and druids?) use conditional magic.
These two systems are but a small part of the magic of the cleric class (and related classes). The new edition of D&D will probably present a generic system as D&D has historically done, which can be modified somewhat to suit different worlds. I do hope, however, they they make it easy for these distinct visions of divinity to be mechanically bound to the setting.
Certain classes are even linked to the role of the deities in the game. The 4e Invoker class is essentially a prophet compared to the cleric's priest. I use these in the sense of the Hebrew bible and the ancient near east, where the priests worked the temple and prophets were charismatic leaders who claimed to speak directly for their deity, often leading small bands of devoted followers. If the deities are all interventionist and use their churches and clerics to intervene, there isn't much space for a distinct prophet class. Conversely, in a game where deities are largely aloof, a prophet who is called to reform the church, lead the chosen to safety, or combat the deity's enemies becomes very different and viable class from the ritual-prayer priest.
Ultimately, the state of divine magic in D&D is a prime case for wedding the rules to the system. I hope the designers of the new edition keep this in mind.