Announcing spells and paying their costs

[Polynomial P]

From what I understand, if a player has 4 artifacts in play, one of which is a lotus petal, he may announce Thoughtcast with affinity for 4, then sac the lotus petal to pay for the cost of the spell at  .

However, if the lotus petal is a lion's eye diamond instead, the same thing cannot be done. Is that because of the text on LED "Play this ability only any time you could play an instant" whereas the Lotus petal does not have that qualifer text?

[Limbo]

You are right in your assumption. As you can see in this topic you first determine cost, then you pay it. In the case of LED, you first need to create the mana before anouncing the spell, which is difficult

(Unless using yawgmoth's will of course, but in that case, the LED wouldn't give you a discount on the thoughtcast if you crack it to cast the thoughtcast)

[Luiggi]

From what I understand, if a player has 4 artifacts in play, one of which is a lotus petal, he may announce Thoughtcast with affinity for 4, then sac the lotus petal to pay for the cost of the spell at  .

Another relevant example that was particularly common in pre-Affinity-bannings Standard: if you have 4 artifacts in play, one of which is Chromatic Sphere, you can announce Thoughtcast, locking its cost at , and then pay for it by filtering one mana through your Chromatic Sphere, netting you an extra card in the process, .

Regarding Lion's Eye Diamond, yes, this trick doesn't work because Wizards errata'd it and added the "Play this ability only any time you could play an instant." text. Back in the day you used to be able to announce a spell, thus removing it from your hand, and then pay for it with Lion's Eye Diamond. I remember abusing this interaction in old Extended decks like PandeNought, where you'd want to pay for a Yawgmoth's Will that you had in hand with an LED, then replay it from the graveyard along with stuff like Pandemonium and Phyrexian Dreadnought, that would make for a very quick kill!

Luiggi

[rvs]

(Unless using yawgmoth's will of course, but in that case, the LED wouldn't give you a discount on the thoughtcast if you crack it to cast the thoughtcast)

So, because of Yawg's Will the rules of casting stuff changes? I'd say you are quite wrong sir!

[Limbo]

(Unless using yawgmoth's will of course, but in that case, the LED wouldn't give you a discount on the thoughtcast if you crack it to cast the thoughtcast)

So, because of Yawg's Will the rules of casting stuff changes? I'd say you are quite wrong sir!

I will lend you my brain-functions for a second and make you think of the possibility of a thoughtcast in the graveyard, which can be cast using the LED and Will's ability, but as you need to still crack the LED before announcing the thoughtcast, it still does not provide a discount. Sir.

[rvs]

(Unless using yawgmoth's will of course, but in that case, the LED wouldn't give you a discount on the thoughtcast if you crack it to cast the thoughtcast)

So, because of Yawg's Will the rules of casting stuff changes? I'd say you are quite wrong sir!

I will lend you my brain-functions for a second and make you think of the possibility of a thoughtcast in the graveyard, which can be cast using the LED and Will's ability, but as you need to still crack the LED before announcing the thoughtcast, it still does not provide a discount. Sir.

Indeed, which is why your initial statement was wrong. And confusing.

[waSP]

Rudy, I would think that the Will would not be cast using LED but rather the Thoughtcast would be cast using the Will.  The English language declares his sentence passable and you repugnant.

[Limbo]

Limbowned AND Waspowned.