Frege's distinction between Sense and Reference serves to deal with a problem in Identity statements. As Leibniz's Law states about identity, “those things are the same of which one can be substituted for another without loss of truth”. This usually doesn't seem to pose a problem, however if we consider the statements
(2) The RZA is the man with the iron fists
we realize that they don't possess the same value for inferential knowledge acquisition. While we can infer statements of the form (1) from the law of identity, we require further premises for (2). Frege therefore states that this difference in cognitive value results from a difference in the 'mode of presentation', which results in two differing Senses with the same Reference. While two different senses such as 'RZA' and 'the man with the iron fists' can have the same reference, the same sentence can refer to different senses. For example, "Prepare these herbs" refers to something different when RZA says it than it does when said by the man with the iron fists.