Obliged and obligated
First things first: I prefer obliged, always.
“Obliged” is always correct, and “obligated” sometimes is. Both have been in the language for several centuries. In “classical” literature, here’s obliged, and here’s obligated. Of course obliged is more common there.
There are some differences:
- Obligated means only a legal/physical (etc.) constraint, while obliged is used for both legal/physical and moral “constraints”. Rather, someone feels obliged, and an obligation is more explicit, like an oath or the law:
- I feel obliged to help her ≈ I thought I should help her ≈ I feel as though I ought to help her
- I was obligated to help her ≈ It was my duty to help her ≈ I had promised her I would help ≈ I owed her a favor ≈ She kept her end of the deal and now it is time for me to uphold my end.
Note that the sense of “obliged” above is only a possible sense that “obligated” doesn’t have; obliged covers both senses.
- AHD says: “Oblige and obligate are interchangeable in the sense of genuine constraint, but not in instances involving a sense of gratitude for a service or favor. A person is obliged (not obligated) when he feels a debt of gratitude and nothing more; he is obligated (or obliged) when under a direct compulsion to follow a given course.”
[From an alt.usage.english thread.]
The plain and simple difference is that “obliged” is always correct, and “obligated” is sometimes correct but it grates on my ears and those of several others.