What are the differences between combat damage, direct damage, and loss of life?

Question

From reading the rules it would appear there are two kinds of damage and then straight loss of life:

118.3 If an effect causes a player to gain or lose life, that player's life total is adjusted accordingly.

From reading that I would guess that effects like Extort are not sources of damage. You simply lose the life.

119.2a Damage may be dealt as a result of combat. Each attacking and blocking creature deals combat damage equal to its power during the combat damage step.

So damage from creatures during combat is combat damage.

119.2b Damage may be dealt as an effect of a spell or ability. The spell or ability will specify which object deals that damage.

And that is direct damage from an object.

So the arguments are these:

Does loss of life as outlined by rule 118.3 (at top) count as being dealt damage? Do triggered abilities that redirect or reduce damage effect loss of life?

My second related question: You put Arcane teachings on a Blinding Angel and tap her to deal one damage to your opponent. Am I right in saying that because the damage was direct damage (not dealt during combat) then the triggered ability of preventing the combat phase of the damaged player is not triggered?

Answer 1

This is cleared up in rule 118.2:

Damage dealt to a player normally causes that player to lose that much life. See rule 119.3.

So you actually have it backwards. Damage to a player is loss of life, not the other way around. When a player is "dealt damage," they lose that much life. (See below for more on "normally.") This is emphasized in rule 119.1a:

Damage can't be dealt to an object that's neither a creature nor a planeswalker.

Spells that specifically say "lose life" cannot be reduced by spells that redirect damage. Damage is caused as "a result of combat" (119.2a) or "as an effect of a spell or ability" (119.2b). Spells that cause loss of life do not cause damage. Instead, they go around damage and just cause the loss of life. There are two ways to cause damage (quoted above as combat damage and damage from spells), and when these objects would inflict damage on a player, that player loses that much life.

If a player takes damage, they lose that much life; if a player loses life, they lose that much life. Additionally, if a creature takes damage, it takes that much damage; creatures do not lose life. Think of life as the currency of players, which damage can impact in a negative way.

This distinction between damage and loss of life is important. They are intentionally kept separate for cards like Griselbrand. The designers wouldn't want you to be able to prevent the loss of life caused by his ability by casting a simple damage reduction spell, like Reflect Damage, so loss of life is kept as a separate concept.

If a triggered ability says "whenever a player is dealt damage," it would not trigger when that player is affected by a spell that causes loss of life.

In regards to the Blinding Angel example, you are correct. Blinding Angel did not deal combat damage so its ability would not trigger.

---

The word "normally" in rule 118.2 refers to one way in which damage is modified, laid out specifically in 119.3b. This rules lays out an important exception to loss of life:

Damage dealt to a player by a source with infect causes that player to get that many poison counters.

This is an exception; players lose life when they are dealt damage 99.9% of the time.

Answer 2

The relationship can be summed up by two rules:

119.2a Damage may be dealt as a result of combat. Each attacking and blocking creature deals combat damage equal to its power during the combat damage step.

119.3a Damage dealt to a player by a source without infect causes that player to lose that much life.

So combat damage is a special subset of damage and non-infect damage to a player causes life loss. Neither of the reverse statements are true. There are many ways to deal damage without it being combat damage. There are also many ways to cause a player to lose life without that player taking damage.

119.2a is the definition of combat damage. To count as combat damage (such as for Fog or Curiosity), the damage must be dealt as a result of combat, not just during the combat phase. This is specifically damage dealt by attacking and blocking creatures during the turn-based action at the beginning of a combat damage step (see below for more details).

119.3a is why damage to a player changes their life total. Damage and life loss are two totally separate game mechanics, joined only by this single rule. There is nothing to make the relationship go the other way. So, for example, Lightning Bolt will trigger the ability on Exquisite Blood, but Circle of Protection: Black cannot prevent the life loss from Kaervek's Spite.

---

Details on combat damage

510.1. First, the active player announces how each attacking creature assigns its combat damage, then the defending player announces how each blocking creature assigns its combat damage. This turn-based action doesn't use the stack.

510.1a Each attacking creature and each blocking creature assigns combat damage equal to its power. Creatures that would assign 0 or less damage this way don't assign combat damage at all.

510.2. Second, all combat damage that's been assigned is dealt simultaneously. This turn-based action doesn't use the stack. No player has the chance to cast spells or activate abilities between the time combat damage is assigned and the time it's dealt.