If you have a book to publish, it is ethically OK to submit your book
proposal to more than one publisher (preferably informing each publisher
that you are submitting the work elsewhere for consideration). However,
regarding the publication of scientific papers it is considered
unethical to submit your work to more than one journal at a time. In
their "Instructions to Authors", most journals make this a condition of
acceptance for review.
This is a nice case for the application of game theory. If journals
are chosen carefully it should be quite difficult for a cheat to be
detected. Since reviewing times are often more than two months, the
cheat gains at least a two month advantage over the non-cheat, if the
paper is rejected by the first journal. There is much talk about
competition and "publish and perish". Is a system which favours cheats
necessarily best for the advance of science? How do publishers justify
maintaining their uni-submission policy?
Sincerely, Donald Forsdyke