Richard Garfield, Ph.D. — ruling 1

Richard Garfield, Ph.D. essentially makes you play a variant of the Magic game called “Mental Magic.” Here’s how the game works. Whenever you cast a spell, you reveal the card to all players and choose any other card (see below for the cards that you can use) that has that card’s mana cost. (Note that color very much does matter.) That spell can then be cast as though it was the chosen card. You aren’t allowed to choose the same card twice.

Richard Garfield, Ph.D. — ruling 2

By default, you are limited to cards legal in the format you’re playing. If you’re playing Draft or Sealed Deck, you can name any card available in the format you’re playing. If you’re playing with Unsanctioned decks, anything goes. Discuss with your playgroup if you’d prefer to modify or eliminate these limitations.

Richard Garfield, Ph.D. — ruling 3

Playing cards as though they were other cards is optional.

Richard Garfield, Ph.D. — ruling 4

Each Richard tracks its own list of played cards. If one leaves the battlefield and another enters, cards previously played under the first Richard are available once again.

Richard Garfield, Ph.D. — ruling 5

If more than one player controls a Richard Garfield, Ph.D., the cards one player plays has no effect on the other players. For example, each player could play Savannah Lions as a Swords to Plowshares this way.

Richard Garfield, Ph.D. — ruling 6

The same is true if Richard Garfield, Ph.D. changes controllers. If you play a Savannah Lions as Swords to Plowshares, then an opponent gains control of Richard Garfield, Ph.D., that player can then do the same.

Richard Garfield, Ph.D. : règles, fonctionnement et interactions (MTG)

Richard Garfield, Ph.D. is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

You may play cards as though they were other cards of your choice with the same mana cost. You can't choose the same card twice. (Mana cost includes color.)

How it works : Richard Garfield, Ph.D.

Original English text — Wizards of the Coast / Scryfall

#1February 29, 2020· Wizards of the Coast
Richard Garfield, Ph.D. essentially makes you play a variant of the Magic game called “Mental Magic.” Here’s how the game works. Whenever you cast a spell, you reveal the card to all players and choose any other card (see below for the cards that you can use) that has that card’s mana cost. (Note that color very much does matter.) That spell can then be cast as though it was the chosen card. You aren’t allowed to choose the same card twice.
No other card is named in this ruling.
#2February 29, 2020· Wizards of the Coast
By default, you are limited to cards legal in the format you’re playing. If you’re playing Draft or Sealed Deck, you can name any card available in the format you’re playing. If you’re playing with Unsanctioned decks, anything goes. Discuss with your playgroup if you’d prefer to modify or eliminate these limitations.
No other card is named in this ruling.
#3February 29, 2020· Wizards of the Coast
Playing cards as though they were other cards is optional.
No other card is named in this ruling.
#4February 29, 2020· Wizards of the Coast
Each Richard tracks its own list of played cards. If one leaves the battlefield and another enters, cards previously played under the first Richard are available once again.
No other card is named in this ruling.
#5February 29, 2020· Wizards of the Coast
If more than one player controls a Richard Garfield, Ph.D., the cards one player plays has no effect on the other players. For example, each player could play Savannah Lions as a Swords to Plowshares this way.
No other card is named in this ruling.
#6February 29, 2020· Wizards of the Coast
The same is true if Richard Garfield, Ph.D. changes controllers. If you play a Savannah Lions as Swords to Plowshares, then an opponent gains control of Richard Garfield, Ph.D., that player can then do the same.
No other card is named in this ruling.