Preterism sees all as having been fulfilled in the first century, especially in the events of AD70. Those events are seen by Christadelphians as a small fulfilment of some Bible prophecies, but the final and major intended fulfilment of the prophecies will be in the last days at the return of the Lord Jesus Christ to earth.
The New Testament presents the promises to Abraham as being the Old Testament version of the Gospel (Gal. 3:8). The New Testament begins with the statement that the Lord Jesus is the seed of Abraham (Mt. 1:1). Preterism and various denominations hold that the promises to Abraham were fulfilled in his lifetime and in the subsequent blessing of Israel his seed. This is indeed the case- but there are significant reasons to believe that these fulfilments were only partial fulfilments and not the only fulfillment. The words of promise came to Abraham as prophecy, prophetic words spoken forth from God. There was a simple way to check out the credentials of a prophet: "When a prophet speaketh in the name of the LORD, if the thing follow not, nor come to pass, that is the thing which the LORD hath not spoken: the prophet hath spoken it presumptuously, thou shalt not be afraid of him" (Dt. 18:22). But how could this be, if prophets spoke of things to be fulfilled well beyond their lifetimes? My suggestion is therefore that all prophecies had an initial, primary fulfillment, which was visible in their own lifetime; and these primary fulfilments were the reassurance that the ultimate fulfillment would surely come. Abraham's a classic case; and the promises to David about a "son" and the Kingdom of that son were fulfilled to a limited extent in Solomon, although the New Testament makes it clear that their main fulfillment was to be in Jesus. So all the arguments that the promises to Abraham were fulfilled have merit so far as they go. But there's no evidence presented that these were the only possible fulfilments of those promises.
Abraham was invited to walk around the land of Canaan, in faith that this land would one day be personally his for ever. He therefore lived as a stranger and foreigner in it: "By faith Abraham, when he was called, obeyed to go out unto a place which he was to receive for an inheritance; and he went out, not knowing whither he went. By faith he became a sojourner in the land of promise, as in a land not his own, dwelling in tents, with Isaac and Jacob, the heirs with him of the same promise: for he looked for the city which hath the foundations, whose builder and maker is God" (Heb. 11:8-10). Note the language of inheritance, being "heirs". Something was promised which they didn't then receive. Heb. 11:13,14 are crystal clear: "These all died in faith, not having received the promises, but having seen them and greeted them from afar, and having confessed that they were strangers and pilgrims on the earth. For they that say such things make it manifest that they are seeking after a country of their own". "Not having received the promises" seems more than clear. Acts 7:5 says the same: "[God] gave [Abraham] none inheritance in [the land], no, not so much as to set his foot on: and [yet] he promised that he would give it to him in possession". But God keeps His promises, and Heb. 11:39,40 explains how this will happen: "These all, having had witness borne to them through their faith, received not the promise, God having provided some better thing concerning us, that apart from us they should not be made perfect". The receiving of the promise would occur when all the faithful receive it together, at the same time. Receiving the promise is paralleled with being "made perfect". This will happen when all the faithful together, at the same time, enter into God's Kingdom at Christ's return. "When the Son of man shall come in his glory, and all the holy angels with him, then shall he sit upon the throne of his glory: And before him shall be gathered all nations: and he shall separate them one from another, as a shepherd divideth his sheep from the goats . . . Then shall the King say unto them on his right hand, Come, ye blessed of my Father, inherit the kingdom prepared for you from the foundation of the world . . . And these shall go away into everlasting punishment: but the righteous into life eternal." (Mt. 25:31,32,34,46). The sheep go into the Kingdom together, at the same time. The sheep haven't yet been separated from the goats, the wheat and weeds are growing together until judgment day. Mt. 7:21,22 likewise speak of entering into the Kingdom at judgment day: "Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven".
Whatever primary application these passages may have had to AD70, the Kingdom of God is clearly not fully established- for "flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption" (1 Cor. 15:50). The Kingdom will be fully established at Christ's return. The image vision of Daniel 2 makes this clear. When human history has run its course, then the stone comes to earth and establishes the eternal Kingdom of God upon earth. Thus Paul speaks of "the Lord Jesus Christ, who shall judge the living and the dead at his appearing and his kingdom" (2 Tim. 4:1). In this sense, the Kingdom of God is the "inheritance" of the believers. It's not fully in our possession now- we are "heirs of the kingdom which he hath promised to them that love him" (James 2:5). Sinners "shall not inherit the kingdom of God" (Gal. 5:21). This language of inheritance goes back to the promises to Abraham and his children of eternal inheritance of the earth. Those promises haven't yet been fulfilled- we will all receive them together, at the same time (Heb, 11:39,40) when we are "made perfect". When we read that "For so an entrance shall be ministered unto you abundantly into the everlasting kingdom of our Lord and Saviour Jesus Christ" (2 Pet. 1:10-11), this is language which could've been used to Abraham; for the promises to him were in essence saying the same. The entrance into the Kingdom is yet future. This is "that blessed hope" of which Paul writes; the whole language of "hope" which fills the New Testament is hard to understand if the hope has already been fulfilled. As we know and see all around us, "the whole creation groaneth and travaileth in pain together until now. And not only so, but ourselves also, which have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for our adoption, to wit, the redemption of our body. For by hope were we saved: but hope that is seen is not hope: for who hopeth for that which he seeth? But if we hope for that which we see not, then do we with patience wait for it" (Rom. 8:22-25). Patiently waiting for what we so hope for... this isn't the language of promises of the Kingdom which have already been fulfilled.
Whilst some aspects of the promises to Abraham were fulfilled, a closer reflection reveals that not all of them were fulfilled completely:
1. The promised land was from the "river of Egypt [the Nile] to the Euphrates" (Gen. 15:18). The nation of Israel never occupied this complete territory.
2. Abraham personally was promised the land for ever (Gen. 13:15- to you and to your seed, for ever). This personal promise has never been fulfilled (Acts 7:5; Heb. 11:8,13). The land which Abraham personally walked through was to be his for ever (Gen. 13:17). "To you and to your seed... for ever" occurs again in Gen. 17:8. It was promised to Abraham personally, as his personal eternal inheritance.
3. Joshua brought about an initial fulfillment of the promises but not a full one, "For if Jesus [Joshua] had given them rest, then would he not afterward have spoken of another day. There remaineth therefore a rest to the people of God" (Heb. 4:8,9).
If the promises to Abraham have already been fulfilled, then a few worrying and sad deductions present themselves:
- Seeing Abraham didn't receive the fulfillment of the promises in his lifetime, either God doesn't keep His promises and the whole basis of the Gospel isn't secure at all, or he received them somehow at his death. This latter view not only contradicts the New Testament statements that Abraham hadn't received what God promised him [at least by the time the New Testament was written], but also supposes conscious survival of death. This is contrary to Bible teaching as we've tried to outline in chapter 4 of "Bible Basics".
- If the promises have been fulfilled in the experience of believers today, then "If in this life only we have hoped in Christ, we are of all men most pitiable" (1 Cor. 15:19). But Paul goes on in that context to reason that the Christian hope is of the resurrection of the body at Christ's return, and inheritance of the Kingdom then.