[PatrickHenry]

And another thing: the bare statement "faster than light travel is equivalent to time travel" does not presuppose time travel into the past as you appear to be doing! Time travel into the future raises no causality issues of its own accord.

While waiting for Physicist to comment, I'll play with this one. While I agree that travel into the future raises no causality issues, it's also irrelevant to FTL communications. As has been pointed out, such communications are always received (by the recipient) before the sender's transmission date, and thus they always involve travel into the past. (This is in the context of the ship and the earth being two different frames of reference.) This isn't a "presuposition," as you suggested. Rather, it's an inevitable conclusion of the way we now think the universe is put together.

[AntiGuv]

But "travel into the past" does not raise causality issues unless it is into a past prior to the time of the transmission being replied to! That's the whole point: you need a second inertial frame (i.e., a third reference frame) in order to produce that phenomenon (based on current theory).

[AntiGuv]

As has been pointed out, such communications are always received (by the recipient) before the sender's transmission date...

Yes, but they are recieved by the recipient after the recipient's preceding transmission date!

[sharpblue]

It is emphatically not the case that FTL communications are always received by the recipient before they're transmitted. Depending on the relative state of motion of the transmitter and receiver its possible for the reception event to have earlier or later coordinate times than the transmission. Coordinate times aren't of any great importance though. As far as I'm aware, the construction in my article is the simplest causality paradox arising from FTL in special relativity.