Weinstein was among the first physicists to reject and criticize Albert Einstein'stheory of relativity, contending that "general relativity had removed gravity from its earlier isolated position and made it into a "world power" controlling all laws of nature," and warning that "physics and mathematics would have to be revised." It was Weinstein's writings, and their impact driving public sentiment against Einstein's theories, which led astronomer Wilhelm Foerster to convince Einstein to write a more accessible explanation of those ideas. But, one commentator contends that Weinstein's summaries of relativistic physics were "tedious exercises in algebra."
Philosophical writings
In addition to his work in physics, Weinstein wrote several philosophical works. examined the origins and development of a great many philosophical areas, including the broadest and most far-reaching examination of the theological theory of pandeism written up to that point. A critique reviewing Weinstein's work in this field deemed the term pandeism to be an 'unsightly' combination of Greek and Latin, though Weinstein did not coin the term, nor did he claim to have. The reviewer further criticises Weinstein's broad assertions that such historical philosophers as Scotus Erigena, Anselm of Canterbury, Nicholas of Cusa, Giordano Bruno, Mendelssohn, and Lessing all were pandeists or leaned towards pandeism. Philosophically, Weinstein was attracted to what he called a psychical or spiritual monism, which he believed to be comparable to the pantheism of Spinoza, and wherein the essence of all phenomena could be found entirely in the mind. Though he could see no way around the eventual heat death of the Universe, Weinstein suggested that there existed a fundamental 'psychical energy,' of which a maximum-entropy world would ultimately consist. Weinstein wrote: From this premise Weinstein reasoned that the world must have both a beginning and an end, and that a supernatural force must have initiated it, and so could bring about its end as well: Though he rejected theistic formulations regarding such things, Weinstein found the origin of the Universe to be so problematic that he wrote: "As far as I can see, only Spinozist pantheism, among all philosophies, can lead to a satisfactory solution."
Works
Handbuch der physikalischen Maassbestimmungen. Zweiter Band. Einheiten und Dimensionen, Messungen für Längen, Massen, Volumina und Dichtigkeiten, Julius Springer, Berlin 1888
Die philosophischen Grundlagen der Wissenschaften. Vorlesungen gehalten an der Universität Berlin …, B. G. Teubner, Leipzig und Berlin 1906
Welt- und Lebensanschauungen hervorgegangen aus Religion, Philosophie und Naturerkenntnis, Johann Ambrosius Barth, Leipzig 1910
Die Physik der bewegten Materie und die Relativitätstheorie, Barth, Leipzig 1913
Kräfte und Spannungen. Das Gravitations- und Strahlenfeld, Friedr. Vieweg & Sohn, Braunschweig 1914