If universal reconciliation is true- so that everybody will eventually come to know God because of his son Yeshua, and therefore nobody will have their flesh burned forever and ever- why should we obey God?
There are two things that most universalists generally agree with- they deny that “hell” lasts forever, and they deny that we have a free will. The sovereignty of God- mixed with his desire that all of mankind will know him- means mankind has no other choice but to eventually know him. So by all means, anybody could live in disobedience if their will should lead them down that path; but there is another force at work in us- our love for God.
Our love for God does not come from some magic free will substance. We love God because God prepared us with the ability to love, and “because he loved us first”.
”Beloved, let us love one another, for love is from God; and everyone who loves is born of God and knows God. The one who does not love does not know God, for God is love.” 1 John 4:7-8
The love God provides for us is much too wonderful to reject. We see his plan of reconciliation, and we know that God is good. Therefore, whatever he says is good- and that means his law is good. There is no better way to live our life than to live it according to his word. I think all Christians, and even Judaism, can agree that the life God provides for us now is far superior to any other lifestyle; as the joy he brings to us is far superior to anything the world can provide.
”If ye love me, keep my commandments.” John 14:15
The “if” is not a stipulation; it’s simply the truth. If we love God, then we will understand the perfection of his commandments, and we will desire to obey them. God does not threaten us with physical torture to force us into obedience. He is most certainly to be feared, as a child ought to fear their father; however:
”There is no fear in love; but perfect love casts out fear, because fear involves punishment, and the one who fears is not perfected in love. We love, because He first loved us.” 1 John 4:18-19
Why should we obey God?
Because we love God. It is a real, uncontrollable, unconditional- yet very much explainable- love:
”O how love I thy law! it is my meditation all the day.
Thou through thy commandments hast made me wiser than mine enemies: for they are ever with me.
I have more understanding than all my teachers: for thy testimonies are my meditation.
I understand more than the ancients, because I keep thy precepts.
I have refrained my feet from every evil way, that I might keep thy word.
I have not departed from thy judgments: for thou hast taught me.
How sweet are thy words unto my taste! yea, sweeter than honey to my mouth!
Through thy precepts I get understanding: therefore I hate every false way.” Psalm 119:97-104
Universalism rejects the natural theology of liberalism, wishing to be distanced from much of the modernist religious spirit of the age (a century ago), to recover what it would call Christianity’s true essence. However, this ‘Neo-Orthodoxy’ was at odds with much traditional Protestant orthodoxy and the emerging liberal Protestantism. It would, for example, reject the virtual universalism of the Latter Day Saints who emerged in the early 1800s with ideas of nearly all of humanity being assured of a resurrection and placement in either the celestial kingdom, the telestial kingdom or the terrestrial kingdom.
“Even for ‘the lost’, the tender mercy of God provides a fitting place in His Kingdom, and the opportunity for continuous repentance.” (1)
Such a doctrine left members concerned to be obedient to God and that church (if they wanted the highest level of the kingdom) but somewhat indifferent to being obedient if they had lower ambitions, or quite indifferent if non-Mormons paid them no attention.
I mention this to illustrate that there are shades of teaching about universalism. The full-blown type you state is at one end, but the universalism of Neo-Orthodoxy is somewhat removed from it. Yes, all of the neo-orthodox leaders embraced higher-critical methods of biblical study to some degree or other, rejecting a literalistic interpretation of scripture. But whatever they might believe hell to be (if not merely the grave), would not impact on their reasons as to why obeying God to the extent humans were capable of would be a good thing, or unnecessary.
All I want to do now is quote from a scholarly book that shows differences between Liberal theology and the more cautious views of universalism as proposed by Karl Barth, linking both to the significance of obeying God (or not). This demonstrates two extremes of universal salvation.
"Barth saw both liberal and conservative Protestant theologies as forms of rationalism in that they sought perfect coherence. For Barth, if God is God, then finite thought cannot arrive at a perfectly coherent synthesis of truth about God. It must simply follow divine revelation wherever it leads and be satisfied if it leads into deadends of thought where seemingly opposed truths must be equally embraced. A third important contribution of Barth’s theology lies in the doctrine of salvation. Liberal theology was almost universally universalistic. That is, from Schleirmacher on, almost all liberal Protestant theologians affirmed an ultimate reconciliation of God with all creatures. The tendency was to reject God’s wrath as a primitive notion that Jesus came to dispel by showing God’s fatherhood, which was interpreted sentimentally by most liberals. Hell, damnation, and eternal punishment were relegated to the stockpile of outmoded relics of medieval theology. Even those liberal theologians who stood in the Reformed tradition rejected double predestination and the entire doctrine of election in favour of a sentimental idea of God’s universal fatherhood of all creatures… Barth believed… God’s entire purpose in creation is salvation, and election is an intrinsic part of salvation by grace alone. But Barth calls his doctrine of salvation and election ‘purified supralapsarianism,’ by which he meant that God’s entire purpose in election is love, and although he allows evil from the very beginning, he negates it through Jesus Christ… Does Barth’s doctrine of salvation imply universalism? Is it a twentieth-century form of Origen’s apokatastasis (ultimate reconciliation)? It would seem so. Yet Barth refused to affirm that, and the best interpreters of Barth’s theology disagree about it." (2)
Perhaps diminishing levels of seeing the need to be obedient to God are commensurate with diminishing levels of holding the biblical scriptures to be the word of God. After all, nobody who holds the whole of biblical scripture to be the word of God could arrive at a doctrine of universal salvation. (I’m prepared to back that up with scripture.) And when one false doctrine is taught, all sorts of other error (theological and practical) will start to be adopted too.
(1) John A. Widtsoe, Varieties of American Religion, pp 137-8
(2) Roger E. Olson, The Story of Christian Theology, pp 584-6