The poet of “The Seafarer” does indeed present two opposing viewpoints in his poem. However, there is no doubt which view the speaker espouses, since he is speaking in the first-person for much of the poem. In fact, he begins with this line:

This tale is true, and mine.

He then goes on to tell about his tribulations upon the cold, forbidding sea in lines 8-11:

My feet were cast
In icy bands, bound with frost,
With frozen chains, and hardship groaned
Around my heart.

At first his tale seems to be simply about a man in a boat on a dangerous ocean. But a little later we begin to see that his real concern is spiritual, in lines 64-66:

Thus the joys of God
Are fervent with life, where life itself
Fades quickly in to the Earth.

The speaker appears to be using the ocean as a metaphor for the difficult and treacherous journey that must be made by the human soul.

The other side of the discussion is concerned with the safety and comfort of life as part of civilization. When man exists within the man-made world, he experiences things like this, from lines 48-49.

Orchards blossom, the towns bloom,
Fields grow lovely as the world springs fresh.

The poet is establishing something called a “juxtaposition.” Artists juxtapose when they present ideas side by side for the purpose of contrasting them. The “Seafarer” poet wants to contrast the solitary, spiritually courageous man with the comfort-seeking socially dependent man.

In "The Seafarer," which lines convey the poem's opposing attitudes?

The speaker of the poem is both drawn to the sea and repelled by it. As the poem begins, we sense the latter attitude as he describes his experience battling nature:

In icy bands, bound with frost,

With frozen chains, and hardship groaned

Around my heart. Hunger tore

At my sea-weary soul. No man sheltered

On the quiet fairness of earth can feel

How wretched I was, drifting through winter

On an ice-cold sea, whirled in sorrow,

Alone in a world blown clear of love,

Hung with icicles.

As difficult a mistress as the sea can be, just a few lines later the speaker describes his compulsion to return to the sea again and again:

And how my heart

Would begin to beat, knowing once more

The salt waves tossing and the towering sea!

The time for journeys would come and my soul

Called me eagerly out, sent me over

The horizon, seeking foreigners' homes.