Are the DB_BLOCK_SIZE and PROCESSES parameters optional in the INIT.ORA file

Are  the DB_BLOCK_SIZE and PROCESSES parameters optional in the INIT.ORA file?

My colleagues insist that this is false but this seems to contradict the Oracle documentation that I have found.

About Initialization Parameters and Initialization Parameter Files

When an Oracle instance starts, it reads initialization parameters from an initialization parameter file. This file must at a minimum specify the DB_NAME parameter. All other parameters have default values.

http://docs.oracle.com/cd/E18283_01/server.112/e17120/create005.htm

So is this a documentation bug (is the documentation wrong)?  Is the DB_BLOCK_SIZE and PROCESS parameters really required in the INIT.ORA file.