For the record, I think Pat Robertson spoke very foolishly recently with his remarks about Alzheimer's and Divorce. The following is a great statement from Joni Eareckson Tada regarding the issue.
“Any marriage has its challenges, but add a serious disability and they can, at times, seem overwhelming. This is why God instituted marriage as a lifelong commitment – Heaven knows it requires vows, solemn and serious, to weather a couple through the demands of disability."
“I was dismayed when this week Pat Robertson said to a nationwide audience that Alzheimer's disease is a kind of death that makes divorce justifiable. When a Christian leader views marriage on a sliding scale, what does this say to the millions of couples who must deal daily with catastrophic injuries and illnesses?"
“At the Joni and Friends International Disability Center, we encounter thousands of couples who, despite living with serious disabling conditions, showcase the grace of God in their weakness every day. Marriage is designed to be a picture of God’s sacrificial love for us. Alzheimer’s disease is never an ‘accident’ in a marriage; it falls under the purview of God’s sovereignty. In the case of someone with Alzheimer's, this means God's unconditional and sacrificial love has an opportunity to be even more gloriously displayed in a life together!”Russel Moore offers more helpful words on the error of Robertson's thinking and the reality that marriage is to reflect the relationship of Christ to his church.
Marriage, the Scripture tells us, is an icon of something deeper, more ancient, more mysterious. The marriage union is a sign, the Apostle Paul announces, of the mystery of Christ and his church (Eph. 5). The husband, then, is to love his wife “as Christ loved the church” (Eph. 5:25). This love is defined not as the hormonal surge of romance but as a self-sacrificial crucifixion of self. The husband pictures Christ when he loves his wife by giving himself up for her.
At the arrest of Christ, his Bride, the church, forgot who she was, and denied who he was. He didn’t divorce her. He didn’t leave.
The Bride of Christ fled his side, and went back to their old ways of life. When Jesus came to them after the resurrection, the church was about the very thing they were doing when Jesus found them in the first place: out on the boats with their nets. Jesus didn’t leave. He stood by his words, stood by his Bride, even to the Place of the Skull, and beyond.
A woman or a man with Alzheimer’s can’t do anything for you. There’s no romance, no sex, no partnership, not even companionship. That’s just the point. Because marriage is a Christ/church icon, a man loves his wife as his own flesh. He cannot sever her off from him simply because she isn’t “useful” anymore.