His orthodoxy did not prevent him from admitting the truth of the claims of the Pietists concerning the prevailing perfunctoriness of religious life, which he ascribed to the negligence of orthodox pastors.
He had already begun the publication of his Unschuldige Nachrichten von alten und neuen theologischen Sachen (Wittenberg and Leipzig, 1701 sqq.
In opposition to the proposal that Pietism should be considered the best means of promoting the union of the Lutheran and the Reformed Churches (advocated at the time by the Prussian Government), Löscher published several works, including Ausführliche Historia motuum zwischen den Evangelisch-Lutherischen und Reformierten (3 parts, Frankfort, 1707–08).
The importance of Löscher's part in the Pietistic controversy was not fully recognized until the return to Evangelical doctrine in the nineteenth century.
Löscher took an active part also in the controversy which at that time was being waged against the Roman Catholic Church in Dresden and contributed a number of studies to that cause, notably his Vollständige Reformations-Akta und Documenta (3 vols., Leipzig, 1720–29).