Although early Priestley scholarship claimed that his theological and metaphysical works were "distractions" and "obstacles" to his scientific work, scholarship published in the 1960s, 1970s, and 1980s maintained that Priestley's works constituted a unified theory.
Walaupun studi-studi awal Priestley mengklaim bahwa karya teologis dan metafisiknya merupakan "gangguan" dan "hambatan" terhadap karya-karya ilmiahnya, studinya yang diterbitkan pada tahun 1960-an, 1970-an, dan 1980-an menetapkan karya Priestley yang meneguhkan kesatuan teori.