Why does `arch` output `i386`?

When I run $ arch on my 10.9 2012 MacBook Pro, I get the output i386 The manpage for arch says that the arch command is 2-way universal, 32-bit only However, $ file "$(which arch)" gives /usr/bin/arch: Mach-O universal binary with 2 architectures /usr/bin/arch (for architecture x86_64): Mach-O 64-bit executable x86_64 /usr/bin/arch (for architecture i386): Mach-O executable i386 OTOH, python2.7 is running as a 64-bit executable: $ /usr/bin/python2.7 -c 'import sys; print "%x" % sys.maxint' 7fffffffffffffff Also, the kernel is apparently 64-bit: $ file /mach_kernel /mach_kernel: Mach-O 64-bit executable x86_64 uname agrees: $ uname -m x86_64 ..or does it? $ uname -p i386