In her posthumously published The Life of the Mind, Hannah Arendt distinguished between solitude and loneliness. The former is the condition that makes thought possible; in the latter state, even the consolations of thinking are absent.
“… to be by myself and to have intercourse with myself is the outstanding characteristic of the life of the mind. The mind can be said to have a life of its own only to the extent that it actualizes this intercourse in which, existentially speaking, plurality is reduced to the duality already implied in the fact and the word ‘consciousness,’ or syneidenai–to know with myself. I call this existential state in which I keep myself company ‘solitude’ to distinguish it from ‘loneliness,’ where I am also alone but now deserted not only by human company but also by the possible company of myself.
To be clear, Arendt understands thinking in a rather specific sense. For her, thinking is not mere problem solving or calculation or the pursuit of truth. It is rather the pursuit of meaning and the work of clearing the ground for the possibility of judgment.
That said, it would seem that in our desire to avoid loneliness we are eroding our capacity for solitude, and thus our ability to think.
The allure of our devices lies in the promise of connection. With smartphone in hand, I never have to be alone again. But in this constant connection we lose our taste and capacity for solitude. Moreover, we may find that connection does not necessarily alleviate loneliness. It does not alleviate loneliness because the devices and platforms that mediate connection are explicitly designed to keep us coming back to them. We will keep coming back to them only if we feel we need what they offer; we will keep coming back, that is, if we feel lonely. Furthermore, it is becoming ever more obvious that connection is like a drug we were offered, at no cost, of course, only to keep us coming back for more at ruinous cost to us and great profit to others.
The dark paradox, then, is this: the more we seek to alleviate our loneliness through digital connectivity, the more lonely we will feel. Along the way, we will forsake solitude as a matter of course. Curiously, it may not even be loneliness as a desire for companionship that the design of social media fosters in us. Rather, it is a counterfeit longing that is generated: for stimulation rather than companionship.
In the end, we will be left with the most profound loneliness: perpetually feeling a need for connection that we cannot satisfy and finding that we have not even our own company.
To recap: no abiding sense of companionship, no solitude, no place for thought.
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See also Nicholas Carr’s recent post, How smartphones hijack our minds.
L.M. Sacasas 
This was well said.
“To think is to forget differences, generalize, make abstractions.” (Borges). We need solitude to reflect. Solitude captures the positive connotations of being alone, loneliness the negative ones.
Resonates with William Deresiewicz, lines in The End of Solitude:
”’…. the Internet is as powerful a machine for the production of loneliness as television is for the manufacture of boredom. If six hours of television a day creates the aptitude for boredom, the inability to sit still, a hundred text messages a day creates the aptitude for loneliness, the inability to be by yourself.”
Discussed the difference with my son. I commented that loneliness is a feeling while solitude is an attitude. He responded that one is a choice, the other is not.
That’s very astute.