Infinitive after verbs of perception

The pattern infinitiv po slovesech vnímání (infinitive after verbs of perception) is an advanced Accusative with Infinitive (AcI) construction. It is used to report the direct, physical sensory perception of an action or event.

Structure:

• Main verb of perception (e.g., vidět, slyšet, cítit)
• The perceived entity in the accusative case (acting as the direct object)
• The infinitive of the action verb

Key Rules & Restrictions:

• Passive vs. Active Perception: This construction is traditionally limited to verbs of passive or involuntary perception (vidět, slyšet, cítit). Using an active or voluntary perception verb (such as pozorovat, poslouchat, or sledovat) with the infinitive is prescriptively incorrect or non-standard, though native speakers occasionally use it in casual modern Czech (e.g., sledoval jsem ho hrát). The standard approach is to use a subordinate clause with jak (e.g., Pozoroval jsem ho, jak hraje).
• Word Order: The standard word order places the accusative object before the infinitive (e.g., Vidím ho přicházet), though Czech's flexible word order allows variations for emphasis.
• Object Omission: The accusative object can be dropped entirely if the person or thing performing the action is unknown, general, or unimportant (e.g., Slyšel jsem klepat or Slyšel jsem zpívat).
• Active for Passive: While passive infinitives cannot be used, Czech uses an active infinitive with an omitted subject to translate English passives. For example, Viděl jsem kácet stromy literally means 'I saw [someone] cut down trees,' but translates to 'I saw the trees being cut down.'
• Aspect: The infinitive can be imperfective to emphasize an action in progress (e.g., Viděl jsem ho odcházet) or perfective for a completed action (e.g., Viděl jsem ho odejít). However, the imperfective is the overwhelming default, since perception inherently involves witnessing a process.
• Temporary Actions Only: This pattern is strictly limited to temporary actions or events (stage-level predicates). You cannot use it for permanent states (e.g., you cannot say *Slyším ho mít přízvuk for 'I hear him have an accent').

Alternatives and Related Constructions:
While this infinitive pattern is standard and elegant, it carries a slightly formal or literary flavor. In casual spoken Czech, native speakers frequently default to a subordinate clause with jak (e.g., Viděl jsem ho, jak odchází.).

Be careful when comparing this with a že clause (e.g., Viděl jsem, že odchází.). A že clause is broader and can mean either direct physical perception ('I saw with my own eyes that he was leaving') OR cognitive realization ('I realized that he was leaving'). The infinitive construction, however, strictly guarantees the physical perception reading.

Additionally, this Accusative with Infinitive (AcI) structure is identical to the one used with the causative verb nechat (to let / to have something done), which is extremely common in everyday speech. For example, in Nechal jsem ho odejít (I let him leave), ho is the accusative object and odejít is the infinitive. You can explore this further in the accusative with infinitive after causative verbs pattern.

Finally, do not confuse this AcI pattern with the highly frequent impersonal sensory construction je vidět or je slyšet (e.g., Je vidět Sněžku - 'Sněžka can be seen'). The AcI pattern requires a specific perceiver as the subject (e.g., Vidím Sněžku), whereas je vidět describes general visibility or audibility without specifying who is perceiving it.