LaTeX align environment missing $ inserted - latex

Question

I'm using an Align environment inside of a proof, and I'm getting the error "Missing $ inserted." I've commenting out all but the first line of the align makes the error go away, but I still can't figure out what the problem is. No solution I could find works. Am I missing something?
\documentclass[12pt,letterpaper]{article}
\usepackage{ifpdf, enumerate}
\usepackage{mla}
\usepackage{gb4e}
\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{stmaryrd}
\newcommand{\tuple}[1]{\ensuremath{\left \langle #1 \right \rangle }}
\newcommand{\evaluation}[2][]{\ensuremath{\llbracket #2\rrbracket^{#1}}}
\begin{document}
\begin{proof}
\begin{align*}
\evaluation[\mathbb{M}]{(Mx)(D (x) \& V (x))} = 1 \iff \\
\evaluation[\mathbb{M}]{\lbrack \alpha / x \rbrack (D (x) \& V (x))} = 1 \text{for most constants \alpha} \\
\evaluation[\mathbb{M}]{(D (\alpha) \& V (\alpha))} = 1 \text{for most constants \alpha } \\
\evaluation[\mathbb{M}]{D (\alpha)} = 1 \text{and} \evaluation[\mathbb{M}]{V (\alpha)} = 1 \text{for most constants \alpha } \\
F(\alpha) \in F(D) \text{and} F(\alpha) \in F(V) \text{for most constants \alpha } \\
\intertext{Examining the definitions of the model, we see that there are only four entities that are both in $F(D)$ and $F(V)$: Alice, Bob, Colin, and David. Because this is not more than half of the total twelve entities in the universe, our naive definition of ``most'' is not satisfied. Therefore the statement is false, which implies that the truth value of the origenal proposition is not 1.}
\end{align*}
\end{proof}
\end{document}
Here is what the error message looks like.
./test.tex:24: Missing $ inserted.
<inserted text>
$
l.24 \end{align*}
?

Answer 1

You've missed only one tricky fact: \alpha only works in math mode, so if you replace all occurrences of
\text{for most constants \alpha} \\
(lines 18, 19, 20, 21) with
\text{for most constants }\alpha \\
then your tex will compile sweetly. Also:
\text{for most constants}\ \alpha \\
or:
\text{for most constants $\alpha$} \\
as you already did in line 22 of your code (...$F(D)$ and $F(V)$...).

Answer 2

This answer is not applicable to this exact case, but the given error can also pop up if the "amsmath" package is not being used. It becomes tricky because the whole code looks alright except I had forgotten to add the \usepackage{amsmath} line in the beginning of the document.