Index: src/library/base/man/library.Rd
===================================================================
--- src/library/base/man/library.Rd	(revision 58980)
+++ src/library/base/man/library.Rd	(working copy)
@@ -21,7 +21,7 @@
         character.only = FALSE, logical.return = FALSE,
         warn.conflicts = TRUE, quietly = FALSE,
         keep.source = getOption("keep.source.pkgs"),
-        verbose = getOption("verbose"))
+        verbose = getOption("verbose"), version)
 
 require(package, lib.loc = NULL, quietly = FALSE,
         warn.conflicts = TRUE,
@@ -59,6 +59,9 @@
   \item{quietly}{a logical.  If \code{TRUE}, no message confirming
     package loading is printed, and most often, no errors/warnings are
     printed if package loading fails.}
+  \item{version}{the minimum acceptable version of the package to load.
+    If a lesser version is found, the package will not be loaded and an
+    exception will be thrown.}
 }
 \details{
   \code{library(package)} and \code{require(package)} both load the
@@ -189,6 +192,10 @@
 search()                    # "splines", too
 detach("package:splines")
 
+# To require a specific minimum version:
+library(splines, '2.14')
+detach("package:splines")
+
 # if the package name is in a character vector, use
 pkg <- "splines"
 library(pkg, character.only = TRUE)
Index: src/library/base/R/library.R
===================================================================
--- src/library/base/R/library.R	(revision 58980)
+++ src/library/base/R/library.R	(working copy)
@@ -32,7 +32,7 @@
 function(package, help, pos = 2, lib.loc = NULL, character.only = FALSE,
          logical.return = FALSE, warn.conflicts = TRUE,
 	 quietly = FALSE, keep.source = getOption("keep.source.pkgs"),
-         verbose = getOption("verbose"))
+         verbose = getOption("verbose"), version)
 {
     if (!missing(keep.source))
         warning("'keep.source' is deprecated and will be ignored")
@@ -276,6 +276,11 @@
             	stop(gettextf("%s is not a valid installed package",
                               sQuote(package)), domain = NA)
             pkgInfo <- readRDS(pfile)
+            if (!missing(version)) {
+                pver <- pkgInfo$DESCRIPTION["Version"]
+                if (compareVersion(pver, as.character(version)) < 0)
+                    stop("Version ", version, " of '", package, "' required, but only ", pver, " is available")
+            }
             testRversion(pkgInfo, package, pkgpath)
             ## avoid any bootstrapping issues by these exemptions
             if(!package %in% c("datasets", "grDevices", "graphics", "methods",
@@ -332,10 +337,18 @@
             stop(gettextf("package %s does not have a NAMESPACE and should be re-installed",
                           sQuote(package)), domain = NA)
 	}
-	if (verbose && !newpackage)
-            warning(gettextf("package %s already present in search()",
-                             sQuote(package)), domain = NA)
+        if (!newpackage) {
+           if (verbose)
+               warning(gettextf("package %s already present in search()",
+                                sQuote(package)), domain = NA)
+           if (!missing(version)) {
+               pver <- packageVersion(package)
+               if (compareVersion(as.character(pver), as.character(version)) < 0)
+                   stop("Version ", version, " of '", package,"' required, ",
+                        "but a lesser version ", pver, " is already loaded")
 
+           }
+       }
     }
     else if(!missing(help)) {
 	if(!character.only)