Table with a diagonal line that crosses cells
Here is one way of doing it, using the graphicx
package:
\documentclass[10pt,letterpaper]{article}
\usepackage{graphicx}
\begin{document}
\begin{table}[]
\centering
\caption{My caption}
\label{my-label}
\begin{tabular}{|l|l|l|l|l|l|l|}
\hline
\multicolumn{1}{|c|}{CONCEPT} & \multicolumn{6}{c|}%
{COMPREHENSIVE NOTES\Large\strut} \\ \hline
Man & Substance & Material & Living & Sentient & Rational & Man \\ \hline
Animal & Substance & Material & Living & Sentient & Brutes & Man \\ \hline
Organism & Substance & Material & Inanimate Bodies & Plants & Brutes & Man \\ \hline
Body & Substance & Material & Inanimate Bodies & Plants & Brutes & Man \\ \hline
Substance & Substance & Spirit & Inanimate Bodies & Plants & Brutes & Man \\ \hline
\multicolumn{1}{|c|}{} & \multicolumn{6}{c|}%
{EXTENSIVE SUBJECTS\Large\strut} \\ \hline
\end{tabular}
\vskip-1.17in\rotatebox{14}{\hskip1.5in\vtop{\hsize=3.75in\rule{3.28in}{1pt}}}
\end{table}
and adjust the dimensions to fit your needs. I added a \Large\strut
to adjust the cell padding for the top and bottom cells.
With tikz
\documentclass[a4paper]{article}
\usepackage{tikz}
\newcommand{\tikzmark}[2][]{\tikz[remember picture, overlay]\node[#1,inner sep=0pt,xshift=-\tabcolsep](#2){};\ignorespaces}
\newcommand{\tm}[2][]{\tikzmark[yshift=#1]{#2}}
\begin{document}
\begin{table}[]
\centering
\caption{My caption}
\label{my-label}
\begin{tabular}{|l|l|l|l|l|l|l|}
\hline
\multicolumn{1}{|c|}{CONCEPT}& \multicolumn{6}{c|}{COMPREHENSIVE NOTES} \\ \hline
Man & Substance & Material & Living & Sentient & Rational &\tm[1.8ex]{A} Man \\ \hline
Animal & Substance & Material & Living & Sentient & Brutes & Man \\ \hline
Organism & Substance & Material & Inanimate Bodies & Plants & Brutes & Man \\ \hline
Body & Substance & Material & Inanimate Bodies & Plants & Brutes & Man \\ \hline
Substance & Substance & \tm[-0.9ex]{B} Spirits & Inanimate Bodies & Plants & Brutes & Man \\ \hline
\multicolumn{1}{|c|}{} & \multicolumn{6}{c|}{EXTENSIVE SUBJECTS} \\ \hline
\end{tabular}
\tikz[remember picture, overlay]\draw[thick] (A)--(B);
\end{table}
\end{document}