The first section one gives the rationale for the book by (i) criticizing still surviving tendencies to support outmoded versions of materialism and (ii) outlining the surprising focus of a diverse group of idealist thinkers from Böhme to Schelling, who argued for energy-based theories of matter and life. This book identifies these thinkers as ‘dynamical idealists’. This diverse group arguably provided truer, more unified, and cogent accounts of matter in the context of force and energy than corpuscularian materialism, which is still sometimes uncritically adopted in twenty-first-century literary studies (e.g. new materialism) and by related humanities scholars who denigrate ‘idealism’ as unembodied and detached from material concerns. Emphasizing the more fundamental place of energy, from which they argued that matter emerges, dynamical idealists identified the dimension of reality that underlies phenomena which support materialist views of matter. Discussion of recent physics and ecological thinking are given, arguing that the fundamentals of dynamical idealism are surprisingly consistent with twentieth- and twenty-first-century science on matter and life. The second section outlines this book, grouping the chronologically arranged chapters into three parts. A short third, final section appeals for an end to crude materialist–idealist polarization, to engage a broader and philosophically and scientifically informed energism that can meet the increasing need to pursue ecological thinking and the understanding of matter and life within systems of energy flow.