Shared ground
Psalm 98:7–8 presents praise as cosmic in scope. The poet calls the sea to “roar,” and not only the water but also its “fullness” (everything associated with it) is included. The summons then expands to “the world” and “those who dwell” in it, putting human beings alongside the rest of creation in a single scene of celebration.
The rivers “clap their hands” and the mountains “sing for joy together.” These are human-like images applied to the landscape. The point is not a quiet, inner response; it is loud, public, and shared. The repeated widening (sea → world → rivers → mountains) builds the sense that nothing in creation is outside the praise.
Where interpretation differs
Some readers take these lines as purely poetic personification: nature cannot literally praise, but the poet describes it as if it can in order to magnify the scale and intensity of worship.
Others think the poetry still points to a real feature of the world: creation, as God’s handiwork, meaningfully “answers back” in its own way. On this view, the roaring, clapping, and singing are not conscious speech but genuine participation—creation behaving as it was made to, in harmony with God’s reign.
A smaller question concerns “the sea’s fullness.” Some hear it mainly as sea creatures; others include whatever the sea contains or carries (all it holds), or simply the sea in all its abundance.
Why the disagreement exists
The disagreement comes from how literal to take the human-like actions (“clap,” “sing”) and how much weight to place on the psalm’s figurative style. The Hebrew poetry clearly uses imaginative language, but it can be read either as “only a picture” or as a picture that also gestures toward a deeper reality about creation’s relationship to God.
What this passage clearly contributes
Explicitly, the text claims that praise is not limited to human worshipers: the sea and its contents, the inhabited world and its people, rivers, and mountains are all summoned to join. It also stresses unity—mountains sing “together,” implying one coordinated chorus rather than competing voices.
By theological inference, the passage supports the idea that God’s rule and worthiness of praise extend over the entire created order, and that human praise fits within a larger, world-sized celebration (compare Psalm 96:11).