The goal of this thesis is to render an ontological inquiry possible by removing four groups of viewpoints which stand in its way. The process of removing the obstacles to an ontological inquiry can be deemed negative ontology, while the very ontological inquiry in question, once it is made possible, can be called positive ontology. Hence, this thesis deals only with negative ontology as defined above and therefore amounts to the fundamental conditions of possibility of an ontological investigation. The groups of viewpoints that stand in the way of positive ontology are herein referred to as (1) subjectivism, (2) dualism, (3) substantialism and (4) positivism. (1) The first group of viewpoints that obstructs ontology encompasses all epistemological positions which consider subject either as limiting the possibility of grasping everything existing or as conditioning everything existing. By ''possibility of grasping everything existing'' we aim at the possibility to grasp everything that exists only in principio, or in its most general form. Since no epistemology is possible without the notion of subject, the first group of viewpoints is gathered under the umbrella term ''subjectivism''. Hence, the goal of the first part of the thesis is to eliminate subjectivism as a means of conditioning ontology; the goal is to demonstrate that no epistemological position can condition any ontological position, just as no subject can condition the very world, and that only the other way round is possible. This goal will be achieved mainly by critically assessing the subject in its historical interpretations ranging from Locke through Hegel and Schopenhauer to the contemporary philosophy, which will finally render the suspicious notion of subject as a being that encompasses everything, including its own self. This gives rise to the distinction between a transcendental and an empirical subject utilized mostly by Kant, the distinction slightly altered in this work so it fits the descriptions of the spirit and the soul, respectively. It will be demonstrated that a subject, if it should establish any epistemology, must be considered first and foremost as a being, i.e., as something existing. This will lead to the conclusion that a transcendental subject (here deemed the spirit), which should condition existence, is impossible without an empirical subject (here deemed the soul, as well as the body), which, in turn, must itself be a being; therefore, the subject in general is itself conditioned by the very position it should have conditioned: by the very existence. Such a process, since it is demonstrated as a mere petitio principii, renders any effort to establish certain grounds for epistemology fruitless, let alone establishing ontology itself. Furthermore, it will be demonstrated that a transcendental subject without an empirical subject must turn into an absolute subject, which is thence completely equated to the world, i.e., to the totality of beings, whereat we arrive at Fichtean position critically processed in this work. If the absolute subject is absolutely the same as the world, therefrom the possibility of a positive ontological investigation follows, because the notion of the world can, in that case, wholly substitute the notion of subject. For example, in that case, we only have beings to deal with, rather than forms of their representations, or thoughts about them, or pure thoughts, etc. The last part of the elimination of subjectivism tends to prove it is possible to know the general form of beings notwithstanding our subjective limitations, thereby abolishing those elements of Kant‟s philosophy whose goal was to restrict the field of ontology. If we may assume something ''ungraspable'', ''unthinkable'' or ''ineffable'' – which can in turn be assume only if we grant Kantian position – we must still consider it as something, i.e. as a being, i.e. as something that shares at least the most abstract form with the graspable, thinkable and effable. Finally, this will lead us to the conclusion that it is impossible to pick an epistemological position which can ultimately condition ontology; just the opposite, every epistemological position must, in the last instance, have its grounds in ontology. In the end, the said amounts to the position that no epistemology can restrict ontology and no subject can restrict beings, but rather only the other way round. (2) The second group of viewpoints that obstructs positive ontology contains all the historical efforts to divide the world into mutually irreducible categories or spheres. Two prominent examples of this are matter-spirit and matter-form divisions. Our task here is to demonstrate that any such division must, in the end, be reduced to a common ground, the one which consists of the notion of being. If we assume one side of such a division as substantial to the beings in the world, then this side, e.g. matter, becomes equated with the notion of being and thereby redundant. If we assume the existence of both sides of such a division, then they are both subsumed under a more general notion of being, which makes them ontologically irrelevant. If we assume that no side of such a division can ontologically prevail, then we automatically deny the possibility of dividing the world into mutually irreducible spheres. Since such divisions usually come in pairs, like the abovementioned examples, this part of the thesis is regarded as the elimination of dualism. However, pluralistic divisions are herein also disabled, along with the non-neutral monistic viewpoints. Finally, this leaves us only with a neutral monism, which means that all beings share a most general form, regardless of any possible division of beings at a less abstract level. This, in turn, makes a most general investigation – ontology – possible. (3) The third obstacle to an ontological inquiry is herein named substantialism. It pertains to the viewpoints that there is something substantial to beings, which makes every being exactly that being, regardless of whether this substance is immanent or transcendent to the beings in question. This part of the thesis aims to deny such a position. In order to do so, we are introducing the definition of substance, in spite of historical definitions, as a being‟s selfequality. In parallel, we will demonstrate that the historical notion of substance, as something different from a being which makes it exactly that being, does not correspond to the very being in question. The whole proof will be strongly connected to the position which denies the distinction between substantial and accidental properties as ontologically relevant and affirms both concrete and abstract beings as something singular. If we manage to demonstrate all beings as singular beings, we will thereby pave the way for an unbiased and nonhierarchized ontological investigation, i.e. the one that assesses beings regardless of their level of abstraction. In this part of the thesis, a short proof of ontological irrelevance of the notion of conditioning will also be given, all the while keeping the notions of ''substance'' and ''condition'' (or maybe ''reason'', ''cause'', ''ideal'') strictly separate. The ultimate goal of this is to equate, at the most abstract level, any possible notion of substance, ground, reason, condition, etc. with the notion of being. Generally, it will be argued that the notion of being in general can equally be derived from the concrete and the abstract beings; just as well, it will be shown that no difference in the way ''the substance'' is constituted (Plato‟s ''transcendence of the universals'' or Aristotle‟s ''immanence of the universals'') can make an impact on the most general determination of beings. (4) The fourth and last part of the thesis deals with, historically, rather a novel viewpoint which stands in the way of a positive ontological inquiry. This viewpoint is known as positivism or, more precisely, logical positivism or neo-positivism. Its main premise denies meaningfulness to ontological statements and notions, such as ''being''. If we are asserting that ontology is possible, then we have to prove its main notions and statements to be meaningful. We will do so using the definition of meaning as ''that which points to something else rather than to itself''. Starting with this definition, it is possible to demonstrate ontological statements and notions as meaningful if they are only pointing to something else, and not to something obviously and tautologically contained in their own selves. In the process, we will distinguish between ''direct tautologies'' (such as ''A=A'', ''airplane is airplane'', ''4=4''), which are meaningless, and ''indirect tautologies'' (such as ''A=B+C'', ''A=B'', ''airplane is a powered flying vehicle with fixed wings and a weight greater than that of the air it displaces'', ''4=2+2''), which are meaningful. An example of a meaningless ontological statement is ''being is'', because it points only to itself, while an example of a meaningful ontological statement is ''being is not infinite'', because it points to something else, not already assumed under the notion ''being''. Likewise, an example of a meaningless ontological notion is the definition of being such as ''being is that which exists'', while an example of a meaningful ontological notion is the definition of being such as ''being is that which is determinate''. In the end, it is demonstrated that the most general notions and statements are not meaningless merely due to their generality; they can be meaningless only due to their lack of ability to indicate. Therefore, if it can be demonstrated that they possess the ability, they are also demonstrated as meaningful.