I am trying to use the first bit of code in this answer to use paragraph like a subsubsubsection.
The problem is that there is a conflict with sectsty - without this the output is exactly as in @GonzaloMedina's answer. When I add sectsty the line break between the paragraph title and the following text disappears, as in the image below. How can I reinsert the line break?

\documentclass{article}
%Sectioning and headings
%------------------------
\usepackage{titlesec}
\usepackage{sectsty} % put section headings in sans-serif font
\setcounter{secnumdepth}{4}
\titleformat{\paragraph}{\normalfont\normalsize\bfseries}{\theparagraph}{1em}{}
\titlespacing*{\paragraph}{0pt}{3.25ex plus 1ex minus .2ex}{1.5ex plus .2ex}
\begin{document}
some text
\section{Section}
some text
\subsection{Subsection}
some text
\subsubsection{Subsubsection}
some text
\paragraph{Paragraph}
some text
\end{document}

titlesecs macros are absurdly complicated it will probably not contribute to your understanding... – 1010011010 Oct 11 '14 at 08:30