\documentclass[12pt]{article}
\begin{document}
Inductive step-\\
Assume the statement holds for $n \in \left\{ 1, 2, ... n\right\}$
\end{document}
Changing the 12pt in documentclass to something bigger doesn't change the size. Any idea what's wrong?

Am I the only one who thinks that the default font size is too small and the margins are too big?
12ptbeing the largest.extarticleoffers extended font sizes or you can use one of the other classes. You might find that you prefer something likememoiror one of the Koma-Script classes if you want a different default for page margins etc., too. – cfr Sep 12 '14 at 02:09\fontsize{#1}{#2}\selectfontand use the geometry package to adjust the margins. – azetina Sep 12 '14 at 02:10