Across:
   1. Famous thinker and initially 19 author, really cross (4)
   3. Experiment on river using machines (10)
  10. Observe soldier having ultimately tragic rationale (5)
  11. Author of "3 Society and Its 12" backing Zagreb mob, an ugly group (9)
  12. Tense reading of will? (6)
  13. Had hope beating despair (7)
  16. In so turning screw, I secure (taking top to right) (9)
  18. Instances where antisemitism's essentially turned around (5)
  20. Such a nerve, changing topic! (5)
  21. Soccer rarely involves final climax (9)
  22. Queens there knew Roy was kinky (3 4)
  24. TISM, if playing, would be nonconformist (6)
  28. Come to pass reprint as original (9)
  29. Happen to remove right to guarantee (5)
  30,31. Publisher's job in White House? (10 4)
Down:
   1. Troublemaker with Y chromosome? (10)
   2. Flying moth's grit at one end of the spectrum (9)
   4. Part of speech that 27 unkindly delivered (4)
   5. Having fallen on deaf ears, perhaps, 11's first three directions were dismal start (10)
   6. In Lesotho mist, I continue following Aquinas scholar (9)
   7. I'm sad to miss out on large soak (5)
   8. Caper about, Karl! (4)
   9. One of your 1 across? They say 1 across had one! (4)
  14. Having fine taste since grind improved (10)
  15. Selection of torments, as fitting (10)
  17. Joker at heart? A crazy man's joking put every other couple out as his 19 appeared in the 22 18 and 30 31 (9)
  19. Document I might write as I foment trouble? (9)
  23. Tests biggest possible turns between points (5)
  25. Concept album's first half lacks solid opening (4)
  26. Soaks coming back for grub (4)
  27. He argued that there should be no movement in disaster zone (4)