Hello R-help, I recently spent a lot of time debugging a program, and the problem turned out to be my own misuse of the det() function. A simple recreation of the problem would be X <- diag (c(2,2,2)) det (X,log=TRUE) ## returns 8 as opposed to log 8 I had simply assumed that (along with many other basic R functions, such as dnorm etc) det can take an argument of log=TRUE and give you the log of the answer. At the very least, if it didn't do this, then I would get an "unused argument" error. The argument "log=TRUE" wasn't used (because now I have looked at the code for det, I see it supplies its own argument to determinant()) so is it not possible to return this error? I guess it is something to do with the way "..." behaves. Alternatively, is there a way for me to set up R so that it will tell me if arguments to functions with "..." aren't really being used? Many Thanks James Lawrence.