Friedrich Schleiermacher (1768–1834) was a German Protestant theologian and philosopher that is frequently called the "Father of Liberal Protestantism." Schleiermacher is arguably the most influential theologian after John Calvin and before Karl Barth, and his most influential books are On Religion: Speeches to its Cultural Despisers and his systematic theology, The Christian Faith. Schleiermacher assumed the philosophical conclusions of his day, especially of Hegel and Kant, and worked out his entire theological program based upon them. Perhaps Schleiermacher's most influential idea, is his definition of God as "a feeling of absolute dependence" that he formed from a Hegelian-esk triad of Knowing (thesis), Doing (anti-thesis) and Feeling (synthesis), and this emphasis on feeling places Schleiermacher into the Pietistic tradition.
Many Conservative Protestants today, especially within American Evangelicalism, regularly define themselves in reactionary opposition to Liberal Protestantism, by asserting they posses a modernistic certainly in their knowledge of God that is guaranteed by the Bible and rationalism (the Knowing thesis alone), and they are quick to label Liberal Protestantism as outside the bounds of orthodox Christianity. In a country that highly values "Liberty" and "Freedom", it is extremely odd to hear American Evangelicals label anyone a "liberal" (as if that was the worst term that they could name-call someone) who says anything sounding like Liberal Protestantism. And there are many voices that are quick to label anyone who identifies with Liberal Protestantism as apostates, false teachers, heretics, deniers of the faith, dangerous, and other colorful phrases. (As you may guess, I'm not a fan of divisive Christians in any tradition).
As the so-called "Father of Liberal Protestantism", many have declared that Schleiermacher was not a real Christian. And if you disagree, or if you can even 'schleiermacher' then you are already liberal as well! Surprisingly, Schleiermacher's greatest opponent was also his proponent. Karl Barth is frequently described as the person who answered the problems that Schleiermacher raised, and Barth answered Schleiermacher by going through Schleiermacher's theology rather than around it (like Conservative Protestants). Barth deeply disagreed with Schleiermacher's theology, yet Barth highly respected Schleiermacher at the same time.
In Karl Barth's 19th Century Protestant Theology, he includes a long essay on Friedrich Schleiermacher, in which Barth expresses his admiration of Schleiermacher, and appeals to Schleiermacher's death bed experience, to assert that Schleiermacher was truly a Christian theologian. Schleiermacher's last meal with the Lord's Supper, which he celebrated on his death bed with his family. Schleiermacher substituted water for wine in the Eucharist, partly because his doctor had forbid him from drinking wine. The question is frequently raised whether this last meal was truly the Lord's Supper, because of this substitution (again this is an odd protest by American Evangelicals who frequently substitute grape juice or rarely ever celebrate the Eucharist at all). Karl Barth defends Schleiermacher by reminding us, that it was Schleiermacher's last wish, and last meal, to celebrate the Lord's Supper (and this is more noble request than most self-proclaimed 'real' Christians seek on their death beds). So Barth argues, based on this last meal of Schleiermacher, we may know that Schleiermacher is truly our brother in Christian.
Karl Barth describes Schleiermacher's last meal as follows:
Schleiermacher, as we know, on his death-bed celebrated Holy Communion with his family: with water instead of wine, which the doctor had forbidden him to drink, and recalling that Christ, in blessing wine, had also blessed water. It can be asked whether the water in the wine was blessed in order that in the last resort it could take the place of wine, or whether it all ceases to be the Lord's Supper when the one is exchanged for the other in this way. But there can be no doubt of the fact that Schleiermacher wanted to celebrate the Holy Communion. He wanted in his Christology, whose content might perhaps be compared with the water, to proclaim Christ. And the fervour with which he did it, as a dogmatician and preacher, is also beyond all doubt in the minds of all who know him. If anyone was most deeply in earnst in this matter then it was Schleiermacher. That cannot of course be regarded as the last word upon the subject; the theological question of truth must remain open here as everywhere, even in the face of the greatest personal sincerity, which cannot be overlooked, just as we must bear in mind the other indications. Ultimately we can only believe that Schleiermacher, too, was a Christian theologian; that, I repeat, is something he has in common with Luther and Calvin and (lest it be forgotten!), upon the lower plane, with all of us. 
Related: Death, Eurchasist, Friedrich Schleiermacher, Karl Barth, lord's supper, Protestant Theology in the Nineteenth Century: Its Background and History