U članku razmatram život i rad u domaćoj historiografiji posve zanemarenog no u svoje vrijeme uglednog zagrebačkog liječnika dr. Karla Marchesija, koji je tijekom 1920-ih i 1930-ih godina u domovini, a zatim i u Sjedinjenim Državama, gdje emigrira 1950. godine i ostaje do svoje smrti, ostvario zavidnu 'ortodoksnu' liječničku karijeru interniste i pionira medicinske hipnoze, ali također i onu 'heterodoksnu', kao jedan od obnovitelja i glavnih protagonista spiritističkog pokreta te lidera parapsiholoških istraživanja u Hrvatskoj, a nakon toga u Sjedinjenim Državama i kao suradnik Josepha Banksa Rhinea na Parapsihološkom laboratoriju pri Sveučilištu Duke, s kojim je uspostavio suradnju iz domovine još 1938. godine. Članak je je podijeljen u dva dijela, a u ovom prvom dijelu ponajprije se rekonstruira bogat životopis dr. Karla Marchesija, a zatim njegova uloga u kontekstu spiritističkog pokreta u Hrvatskoj tijekom 1930-ih. Pri ovoj raščlambi, posebna se pažnja posvećuje širem socijalno-historijskom kontekstu geneze i razvoja spiritističkih pokreta i stremljenja poglavito na tlu Hrvatske, kojih je dr. Marchesi bio tipični egzemplar, što je samo po sebi historiografski, povijesno-znanstveno, filozofski i teološki također u nas gotovo pa posve nepokriveno. U drugom, sljedujućem dijelu članka razmotrit će se 'heterodoksni' rad dr. Marchesija u parapsihologiji te hipnotizmu, gdje je ovo potonje vremenom iz kontroverznog preraslo u legitimnu znanstvenu disciplinu medicinske hipnoze, u kojoj će dr. Marchesi ostaviti zapaženog traga na svjetskoj razini. Također, u drugom dijelu rada reflektirat će se općenito odnos 'ortodoksnog' i heterodoksnog', 'znanosti i pseudoznanosti' u svjetlu relevantnih spoznaja moderne povijesti i filozofije znanosti, nasuprot nekim uvriježenim, ali pogrešnim narativima o ovom odnosu. In this article, I discuss the life and work in Croatian historiography of the completely neglected but at the time prominent Zagreb physician Dr. Karl Marchesi, both in respect to his orthodox medical career as an internist and pioneer of medical hypnosis in his homeland during the 1920s and 1930s and then in the United States, where he emigrated in 1950 and remained until his death, and his heterodox career as one of the restorers and main protagonists of the spiritist movement and leaders of parapsychological research first in Croatia and then in the United States as a close collaborator of Joseph Banks Rhine at the Parapsychological Laboratory at Duke University, with whom he established a collaboration already from his homeland in 1938. The article is divided into two parts, and in this first part I reconstruct the rich biography of Dr. Marchesi and analyze his role in the Croatian spiritist movement during the 1930s. In this analysis, particular attention is paid to the broader socio-historical context of the nature and genesis of the spiritist movements, especially in Croatia, of which Dr. Marchesi was a typical exemplar, and which is by itself also a fairly neglected topic of the histories of science, philosophy, and theology in Croatia. The second part of the article will discuss Dr. Marchesi’s heterodox work in parapsychology and hypnotism, the latter having grown from a controversial to a legitimate scientific discipline of medical hypnosis in which Dr. Marchesi has left a noticeable international mark. Also, in the second part of the article, I will reflect on the general relationship between ‘orthodoxy’ and heterodoxy’ in science, as well as on the relationship between science and pseudoscience in light of the relevant knowledge of modern history and philosophy of science, as opposed to some ingrained but erroneous narratives about this relationship.