～とはかぎらない— Not Always the Case

• 高い物が良い物だとは限らない。

  Takai mono ga yoi mono da to wa kagiranai.

  Expensive things aren't necessarily good things.

  良い物だ + とは限らない denies the generalization, allowing exceptions.

• 努力すれば必ず成功するとは限らない。

  Doryoku sureba kanarazu seikou suru to wa kagiranai.

  Making an effort doesn't always guarantee success.

  成功する + とは限らない says the outcome isn't certain in every case.

• 有名な店がおいしいとは限らない。

  Yuumei na mise ga oishii to wa kagiranai.

  A famous restaurant isn't necessarily delicious.

  おいしい + とは限らない cautions against assuming the rule always holds.

• ・Function: denies that a generalization is always true; leaves room for exceptions.
• ・Often reinforced by 必ずしも at the front of the clause.
• ・は may be dropped in casual speech (とも限らない adds 'nor can we say for sure').

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones ～とはかぎらない is tested against.

• ～べきだ — What One Ought to Do
• ～ずにはいられない — Simply Cannot Resist
• ～ないではいられない — Can't Hold Back
• ～というものではない — Not Necessarily So
• ないことはない — It's Not That You Can't