The author examines the reason (objective, basis, function) of the existence of judicial protection of mere possession, as a separate remedy alongside petitory action, and tests the sustainability of theories in relation to such a reason. In Part 1 (published in this issue) the author presents historical and comparative models of regulation of such remedies, relationship to petitory action, petitory objection, objection of petitory absorption and petitory counterclaim, types of proceedings in which protection is afforded, relationship towards preliminary injunction proceedings and self-help of the possessor, object of the protection, infringement of possession, passive legitimation etc. In some jurisdictions possessory protection is absolute: it is completely independent of the plaintiffs and respondent's right to mere possession and the respondent's better right (especially the non-cumul principle). In others, possessory protection excludes the respondent's better right (relativised possessory protection): as the petitorium absorbet possessorium objection, as a petitory objection of the better right, or as a petitory counterclaim. Such protection is always provisory, and usually urgent, provided in a separate, accelerated (summary) civil procedure; in other cases the judicial procedure applied is general civil procedure, while in the least number of cases the protection is provided by administrative authorities. There is a widespread idea that since the protection only needs to be provisory, that it can be urgent, and since it should be urgent, that it is allowed for it to only be provisory. Urgency and provisory nature are also characteristics of protection of mere possession through injunction to protect possession, but there are significant differences between the two in the basis for protection, coming into effect and nature of effects. Even though their functions differ, the injunction procedure has nevertheless repressed the possessory civil procedure where the latter has not sped up. Urgency and provisory nature also connect judicial possessory protection to protection via permitted self-help. However, their mutual relations differ in different states, due to the fact that possessory self-help is diversely regulated in individual states in respect of the scale of its differences to the general regime of self-defence, state of emergency and self-help, if it is purely defensive or offensive as well, and how much it differs in the case of deprivation of possession than in the case of interference with possession, but also because different models of judicial possessory protection are combined with different models of both general self-help and privileged special possessory self-help. As possessory protection is never the only form of protection from infringement of possession, due to the fact that there is always a slower but final petitory protection, possessory action and self-help are always tied by deadlines. Deadlines are seldom equal for self-help and judicial action. There is no possessory protection today which would be accessible in a longer period after possession has been infringed, such as was the case with actio spolii since the Middle Ages. However, the deadlines differ significantly, from immediate, through thirty days, to one or three years, be they objection, subjective, preclusive or subject to statute of limitation, the same or different for dispossession or interference with possession. Possessory protection is not provided to any possession: in different jurisdictions there are types of possession unprotected due to their type (indirect contrary to direct, joint possession in relation to co-possessors, tabular possession), due to their characteristics (faulty or illegal possessions, the ones which lasted for a shorter period before judicial action than the infringers possession, short possessions, possessions for the reason of simple courtesy), or due to their objects (possession of movables). Judicial protection of mere possession, on the other hand, is not exclusively a protection of possession, because the same type of protection is somewhere provided to non-possession - to detentors and mere detentors. The concept of mere possession (subjective, Roman or objective, German) does not determine the area of application of possessory protection, i.e. which possessions and which nonpossessions shall be protected: there is no significant difference between jurisdictions in that respect depending on the adopted concept of mere possession, but there are differences even within jurisdictions which adopt the same concept of mere possession. Neither is the concept of mere possession in correlation with the model of possessory protection (absolute or relativised). And the model of possessory protection (absolute or relativised) is not in co-relation with a specific notion of infringement of possession: everywhere is possession protection against dispossession and interference and the narrower (traditional, Roman) notion of infringement (aut vi aut clam aut precario) and the wider one (modern, German) notion (unlawful infringement) are seen in both the states familiar with the absolute possessory protection and the ones with the relativised concept. In the state where infringement of possession is understood in a narrower sense possessory protection has become more similar to the protection in states which adopted a wider notion of it, both a wider interpretation of forceful or stealth dispossession or infringement, both by adding other modalities as well (particularly infringement by trickery or fraud). Possession is always protected against the person performing the dispossession or interference with possession, and along its side, addressees of a possessory action or permitted self-help can, in some places, also be this person's universal successors, his/her principals, singular successors, or other persons which simple hold the dispossessed good, be they objectively passively legitimised (irrespective of their good faith) or subjectively and objectively, under harder, or under easier conditions. - Since those and such historical and comparative differences of possessory protection do exist, finally the author lists the issues for which he believes have to be posed in relation to each of these differences when the reason for possessory protection is examined: whether these differences are a reflection of the reason for possessory protection, and in accordance with that, and do they influence the sustainability of theories on the reasons for protection. These issues are addressed in Part 2. of this article (to be published in the next issue).