PurposeThe purpose of this study of this methodological abstraction is erected the nature of the well-being function as evaluative criterion. The well-being function (maslaha) evaluates the interrelationships between long-run investment (real sector), the corresponding financial instruments (financial sector) and the embedded socioeconomic variables and ethical values conveyed by extensive complementarities and participation in a systemic approach of unity of knowledge. Among the financing variables to be selected will be the transformation of debt-instruments into equity instruments. All financial instruments are to be transformed into a holistic participatory pooled portfolio.Design/methodology/approachThe paper establishes the point that, the idea of long-run is appropriately that of a juncture of Islamic change during which the objective of well-being (maslaha) is evaluated (estimation leading to simulation) with long-run investment and Islamic financing instruments on the basis of the Islamic methodological worldview. This methodological worldview is premised on the ontological foundation of the episteme of organic unity of knowledge and the resulting world-system. The Qur’an refers to this foundation of knowledge as Tawhid. Tawhid is used in this paper to mean the Primal Ontological Law of Unity of Knowledge.FindingsThe most critical long-run investment program focused on is poverty alleviation and its equity-based financing instruments that reduce debt progressively to attain sustainable grassroots development with the ability to own, and the social capability to distribute resources and enable the grassroots. The corresponding interaction, integration and evolutionary dynamics of learning that emanate from the interrelationship of poverty alleviation as the focus of long-run investments and their attenuating financing instruments, along with the implications of inter-causal socioeconomic variables and the embedded episteme of unity of knowledge in the well-being function (maslaha). This paper is thus an abstracto-empirical contribution to the literature of Islamic finance, long-run investment and socioeconomic development with global significance.Research limitations/implicationsThe choice of long-run investment for poverty alleviation and the corresponding Islamic financing instruments are summarized by the following Tawhidi epistemic schema (an extractive picture). Upon this epistemic methodological worldview, the entire structure of well-being and sustainability of socioeconomic development lies.Practical implicationsThe paper brings out many of the properties that ought to be the truly moral/ethical and thereby the conformable analytical nature of the model of financing and investment in a combination of short-, medium- and long-term mobilization of resources to attain levels of social well-being as the objective criterion. Empirical work is done to bring the objective criterion to an applied level and to critically examine the work in the same field being carried out by many other ones, including authors and institutions. The empirical work done here can be widely extended to the case of estimating of the maslaha function (well-being).Social implicationsThis paper carries an essentially moral and social perspective in its methodological orientation that is derived from the Islamic epistemological foundations of unity of knowledge (Tawhid) and applied to Islamic finance and investment theory with the well-being objective criterion.Originality/valueThis is an original paper that combines methodological abstraction with applied financing and investment perspectives. Such an abstracto-empirical approach has not been done in Islamic research writings.