<p>A Swiss, C.G. Jung, was a psychological pioneer whose renown in the field of psychoanalysis almost equals that of Sigmund Freud.</p>
<p>^ Why does there need to be a comma after C.G. Jung?</p>
<p>If you remove that comma, the sentence is still grammatically correct, but the noun emphasis changes a bit. Without the comma, the sentence puts the emphasis on GC Jung as the pioneer. With the comma, the Swiss is the pioneer and GC Jung is an appositive. Appositives can be removed from the sentence and the meaning still holds up. You can see examples here: [The</a> Appositive](<a href=“http://www.chompchomp.com/terms/appositive.htm]The”>The Appositive | Grammar Bytes!).</p>
<p>I understand now! Thank you so much!! :)</p>
<p>SATwriter’s explanation is correct. I would, however, add that the omission of the second comma would make more sense here, since the emphasis on “A Swiss” over “C.G. Jung” as suggested by the restrictive apposition of two commas would probably be justifiable only if Sigmund Freud’s nationality were mentioned or the sentence were in the context of a discussion about nationalities in general or Switzerland in particular.</p>