What's the XP cost to learn an unknown 1-dot art in a known arcanoi?

Question

The 20th Anniversary edition of Wraith: the Oblivion describes the mechanic for learning unknown arts at the same rating as a known art (e.g. learning an initiate art, when the common art is known) thusly:

An eligible character who already knows a common art for a given Arcanos rating may also learn the initiate art for the same rating or vice versa. This carries the same experience-point cost as the original dot for that level of the Arcanos.

The section on spending XP gives the following costs related to arcanoi:

Trait	XP Cost
New Arcanos	7
Arcanos	current rating * 3
…	…

From the first paragraph, the "current rating" when there's existing art is not the rating of the arcanos that's written on the character sheet, but the what the rating would have been when first increasing the rating to the art being learned; in other words, 1 less than the rating to be learned.

This seems to leave out one case. What's the XP cost for learning a 1 dot art for a known arcanoi (ignoring any discounts for a guild tutor)?

For example, suppose a wraith had two dots in Argos, both in the initiate arts (Enshroud, Wayfarer's Resolve), and the player wanted the character to learn the 1-dot common art (Weather Eye). It's not a new arcanos, so it shouldn't be the 7 cost. Additionally, having a 1-dot art cost more than a 2 dot art (Phantom Wings would cost 3) doesn't seem reasonable. The only other rule would put the cost at 0 xp (the "current rating", which would be 0 for a 1-dot art, times 3), which also isn't reasonable.

Answer 1

There might not be a definitive answer in the 20th Anniversary rules, but a look at the 2nd edition suggests two options. There, XP costs for arcanoi are the same as in the 20th, but it also has a cost of 4 points for basic arcanoi (which are basically 0-point arts) and thus a cost of 3 XP to get the first dot when the basic arts are known (this is explicitly noted at the bottom of the XP cost chart on p. 228). This 3-point cost could be taken for the 20th Anniversary edition as the cost for 1-dot arts in a known arcanoi. This makes the cost for 1- and 2-dot arts the same, which may not seem entirely balanced, but has precedence (this is also the case in 2nd edition). Additionally, it's relatively cheap, especially with a discount for Guild instruction.

More to the point, the section on Arcanoi in the 2nd edition (p. 133) has near the start an aside on learning "alternate arts", including a table of XP costs. The cost to learn an alternate level 1 art (when the wraith has at least 1 level in the arcanoi) is 1 point. The costs for higher level alternate arts are the same as for learning that level the first time (just as it is in 20th).