A possible benefit of conditions in Common Lisp is more than 25 years worth of implementation experience and full documentation of how the system is structured.

Extensive literature about the language is a defining feature of Lisp.

Conditionals as detailed in Common Lisp the Language, 2nd Edition: http://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node312.html#S...

Hmm, the same argument could be made of GOTOs in FORTRAN.

GOTO's use in Fortran has continued to be deprecated for several decades.

One might say that they are not Fortrany in the way that conditionals are Lispy.

That's non-essential, but certainly nice to have. Thanks for the insight.

That is, of course, the standard argument for dynamic binding in general.

So in CL one could certainly pass a callback via dynamic binding and get the same effect.

The choice to use the condition primitives instead is, then, simply a stylistic one.

For those who wonder whether that is worth a new idiom to learn: the stylistic effect is enormous.

For example, there could be 5 layers of code between a condition handler and the code signaling a "file not found" condition, and the top levels of that stack might not even be aware that they could trigger such a condition or even any condition at all.

In some sense, this is the reverse of Java's checked exceptions. There, you have the problem that an interface declares exception X and Y, and an implementation that wants to throw a Z has to encapsulate that exception into a X or an Y. Here, the intermediate layers _can_ be blightfully unaware of those conditions.

A common use case is to use conditions without registered handlers as "break on exception" breakpoints, with the benefit that the human working with the debugger has more options than "stop execution", "continue and pray" and "tweak some memory, set the PC, go, and hope for the best". For example, if the 'open file' system call has a restart, users can easily fix "oops, that lengthy computation is done, but I mistyped that output file name." error conditions.