I'd love to know why traditional document classes are not including a new line after the \paragraph sectioning command. Maybe there is some typographic history behind it or something (maybe not and this is a totally dumb question), just curious. Searching the web wasn't from help to answer this.
[Tex/LaTex] Why is there no new line after paragraph sectioning commands
sectioningsections-paragraphstypography
Related Solutions
The output of \show cannot be used as you are trying. It says that \subsection is a "long" macro that has no arguments and the replacement text is what follows ->.
The right place where to look is report.cls, where you find
\newcommand\subsubsection{\@startsection{subsubsection}{3}{\z@}%
{-3.25ex\@plus -1ex \@minus -.2ex}%
{1.5ex \@plus .2ex}%
{\normalfont\normalsize\bfseries}}
\newcommand\paragraph{\@startsection{paragraph}{4}{\z@}%
{3.25ex \@plus1ex \@minus.2ex}%
{-1em}%
{\normalfont\normalsize\bfseries}}
The key point that explain the different behavior are: the negative fourth argument of \@startsection for \subsubsection which suppresses indentation of the following paragraph; the positive fifth argument tells TeX that the title will not be "run-in". So
\makeatletter
\renewcommand\subsection{%
\@startsection{subsubsection}{3}{\z@}{3.25ex \@plus1ex \@minus.2ex}%
{-1em}{\normalfont\normalsize\bfseries}}
\makeatother
The second argument to \@startsection tells LaTeX the level of the sectioning command for the purposes of secnumdepth and tocdepth and should stay 3.
Important note
The \makeatletter and \makeatother commands are necessary because we are doing stuff involving the internal command of LaTeX.
Every time a command containing @ in its name has to be used, the code must either be in a .sty file or surrounded by that pair. See What do \makeatletter and \makeatother do? for more information.
Using titlesec:
\documentclass{article}
\usepackage{titlesec}
\titleformat{\paragraph}
{\normalfont\normalsize\bfseries}{\theparagraph}{1em}{}
\titlespacing*{\paragraph}
{0pt}{3.25ex plus 1ex minus .2ex}{1.5ex plus .2ex}
\begin{document}
\section{A test section}
text
\subsection{A test subsection}
text
\subsubsection{A test subsubsection}
text
\paragraph{A test paragraph}
text
\end{document}
Without packages, simply copy the definition of \paragraph from your class and adjust the fourth and fifth arguments of \@startsection; for example:
\documentclass{article}
\makeatletter
\renewcommand\paragraph{\@startsection{paragraph}{4}{\z@}%
{-3.25ex \@plus1ex \@minus.2ex}% original: without the minus
{1.5ex plus .2ex}% original {-1em}%
{\normalfont\normalsize\bfseries}}
\makeatother
\begin{document}
\section{A test section}
text
\subsection{A test subsection}
text
\subsubsection{A test subsubsection}
text
\paragraph{A test paragraph}
text
\end{document}
To have paragraphs with numbering, add
\setcounter{secnumdepth}{4}
to the preamble; to include them in the ToC, add also
\setcounter{tocdepth}{4}
Best Answer
Most latex sectioning commands (below
\chapter) are handled by the internal\@startsectionmacro. This implements two distinct styles of heading display headings that are offset vertically from the following paragraph, and inline headings that are set as the initial part of the following paragraph.The standard classes switch style to inline at the
\paragraphlevel although it is easy to redefine them back if you wish.Inline "headings" are not that uncommon but sometimes "heading" text isn't really a heading but just the first word(s) of the paragraph. The setting is often similar to that of a
descriptionenvironment which is often another alternative markup at this level, there isn't really a hard line between sectional units of a document and a list once you get down to level 5 or 6 headings.