A friend of mine says Buddhism is Pantheistic. She believes that the fundamental message of Buddhism is that there is no self, that we are all manifestations of the same life force, that we're connected by some underlying Substance, etc... I think she has come to this as a result of the scholars she reads, who I imagine, given what she studies, are very Deleuzean (who was himself inspired by Spinoza and his Pantheistic metaphysics). I believe these scholars, and so my friend's impression of the faith, bring metaphysical presuppositions to the table. i.e., Pantheism is what they want to see when reading Buddhist Scipture, and the ambiguity of the texts make possible any metaphysical reading...
More than this though I think Buddhism and Pantheism are inconsistent with each other, and so despite the ambiguity of Scripture we can rule it out completely as part of the Buddhist faith. First, from my admittedly limited studies of Buddhism, I recall a passage where Buddha tells us to abstain from metaphysics; that it is, like so many other things, a distraction. In other words, if Buddha practices what he preaches then Buddha did not engage in metaphysics, and so to think Buddhism has a metaphysical message misses the point, or at least the main point, of the faith.
But this only shows that Pantheism can't be the main message of Buddhism. Even though Buddha didn't actively engage in metaphysics, Buddhism may still have metaphysical relevance... Thus my second and more powerful reason is love. Buddha calls for an all encompassing love. My argument is that if Buddhism is primarily loving then Pantheism is necessarily ruled out as a metaphysical possibility. Pantheism means the only love possible is self love. If we're all the same, if there is no self but simply different facets of the same life force, then the only love possible is self love... Buddhist love, compassionate love, is not self love. No one can feel compassion for oneself. One cannot suffer with oneself... In Pantheism one is necessarily alone in their suffering and compassion is impossible. For compassion to be possible there must at least be two, and as such Buddhism presupposes in its call for compassionate love, if anything, two instead of one. Pantheism is ruled out by love.
If there is a Pantheistic element to Buddhism I think it can be found as a weaker form in two places:
1. In the common fate of every one to suffer and die.
2. In the possibility of an all encompassing love.