Biblical terms, ironically the only thing that is shown to be stirring is a sphinx-like figure that moves itself threateningly. The speaker sees the world's spirit, or "Spiritus Mundi" depicted in the following way:

A shape with the lion body and the head of a man,

A gaze blank and pitiless as the sun,

Is moving its slow thighs, while all about it

Reel shadows of the indignant desert birds.

The gaze of this creature being "blank and pitiless as the sun" clearly summarises the lack of hope for the future that the poet sees. This is of course exacerbated by the ending which alludes to another birth of Jesus but making it very different:

And what rough beast, its hour come round at last,

Slouches towards Bethlehem to be born?

This "rough beast" could symbolise totalitarianism, warfare or inhumanity. Clearly the poem paints a dire prophecy which probably Yeats conceived after the events of WWI which led him to believe that humans were slipping back into their former savage state dominated by chaos.

I think by far the most profound image of the poem that it begins with is of the falcon turning and turning in an ever-widening gyre as it seeks to escape the control and influence of its falconer:

Turning and turning in the widening gyre

The falcon cannot hear the falconer...

If we examine this image carefully, we can say that the falcon and the falconer in their relationship symbolise order and control. However, the breakdown of this relationship clearly suggests that irrationality and chaos is replacing order and control in the contempoary world, as the falcon is not responsive to the falconer and circles further and further away from him. It is this that cuases the loosing of the "blood-dimmed tide" and the drowning of "the ceremony of innocence," two other very strong images that point towards a future of savagery, chaos and violence.