  We provide two criteria for discarding the formality of a differential graded
Lie algebra in terms of higher Whitehead brackets, which are the Lie analogue
of the Massey products of a differential graded associative algebra. We also
show that formality of a differential graded Lie algebra is not equivalent to
the collapse of the Quillen spectral sequence. Finally, we use $L_\infty$
algebras and Quillen's formulation of rational homotopy theory to recover and
improve a classical theorem for detecting higher Whitehead products in Sullivan
minimal models and give some applications.
