diff --git a/TODO.md b/TODO.md
index a436ee8..2007f03 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,10 +1,8 @@
-`barometer-belief.test` -- 在测试中增加书中的叙述 -- 与对 belief-system 的测试相同
-
 # 4.3 Dependencies Explain Contradictions
 
 > https://github.com/cicada-lang/propagator/issues/9
 
-修复对 `MergeConflict` 的使用 -- 如何处理原实现中的 `call/cc`？
+implementation `MergeConflict` without `call/cc`
 
 # 4.4 Dependencies Improve Search
 
@@ -37,6 +35,8 @@
 
 # later
 
+[later] `barometer-belief.test` -- 在测试中增加书中的叙述 -- 与对 belief-system 的测试相同
+
 [later] barometer-belief-system.test.ts -- 理解我们的测试中与书中有差异的地方
 
 - 书中第一个测试只有：
diff --git a/src/belief-system/assimilateBeliefSystem.ts b/src/belief-system/assimilateBeliefSystem.ts
index a913144..8d91c72 100644
--- a/src/belief-system/assimilateBeliefSystem.ts
+++ b/src/belief-system/assimilateBeliefSystem.ts
@@ -1,4 +1,3 @@
-import { type Nothing, isNothing } from "../nothing/Nothing.js"
 import { assimilateBelief } from "./assimilateBelief.js"
 import type { BeliefSystem } from "./BeliefSystem.js"
 
@@ -8,12 +7,8 @@ import type { BeliefSystem } from "./BeliefSystem.js"
 
 export function assimilateBeliefSystem<A, B>(
   base: BeliefSystem<A>,
-  target: BeliefSystem<B> | Nothing,
+  target: BeliefSystem<B>,
 ): BeliefSystem<A | B> {
-  if (isNothing(target)) {
-    return base
-  }
-
   return target.beliefs.reduce<BeliefSystem<A | B>>(
     (result, belief) => assimilateBelief(result, belief),
     base,
diff --git a/src/belief-system/checkConsistent.ts b/src/belief-system/checkConsistent.ts
index fd34f36..8bbb2b1 100644
--- a/src/belief-system/checkConsistent.ts
+++ b/src/belief-system/checkConsistent.ts
@@ -1,17 +1,15 @@
 import { detectMergeConflict } from "../merge-conflict/detectMergeConflict.js"
-import { isRunning } from "../scheduler/run.js"
+
 import { clearScheduledPropagators } from "../scheduler/schedule.js"
 import { log } from "../utils/log.js"
 
 export function checkConsistent(value: any): void {
+  return
+
   if (detectMergeConflict(value)) {
     const who = "checkConsistent"
     const message = "Inconsistent value"
     log({ who, message, value })
     clearScheduledPropagators()
-
-    if (isRunning) {
-      throw new Error(`[${who}] ${message}`)
-    }
   }
 }
diff --git a/src/belief/beliefMerge.ts b/src/belief/beliefMerge.ts
index 6568c7e..afbccfa 100644
--- a/src/belief/beliefMerge.ts
+++ b/src/belief/beliefMerge.ts
@@ -1,4 +1,3 @@
-import type { MergeConflict } from "../merge-conflict/index.js"
 import { merge } from "../merge/index.js"
 import { setIsSubsetOf, setUnion } from "../utils/set/index.js"
 import { Belief } from "./Belief.js"
@@ -24,7 +23,7 @@ import { Belief } from "./Belief.js"
 export function beliefMerge<A, B>(
   content: Belief<A>,
   increment: Belief<B>,
-): Belief<A | B> | MergeConflict {
+): Belief<A | B> {
   const mergedValue = merge(content.value, increment.value)
 
   // 下面刚好是偏序关系中比较两个元素的四种可能：
@@ -45,6 +44,10 @@ export function beliefMerge<A, B>(
     }
   }
 
+  // if (isMergeConflict(mergedValue)) {
+  //   console.log({ who: "beliefMerge", increment, content })
+  // }
+
   if (mergedValue === increment.value) {
     return increment
   }
diff --git a/src/cell/put.ts b/src/cell/put.ts
index 5a1b188..e560dfa 100644
--- a/src/cell/put.ts
+++ b/src/cell/put.ts
@@ -3,15 +3,11 @@ import { schedule } from "../scheduler/index.js"
 import { type Cell } from "./Cell.js"
 
 export function put<T>(cell: Cell<T>, increment?: any): void {
-  try {
-    const newContent = merge(cell.content, increment)
-    if (newContent === cell.content) {
-      return
-    }
-
-    cell.content = newContent
-    schedule(cell.propagators)
-  } catch (error) {
-    console.error({ who: "put", error })
+  const newContent = merge(cell.content, increment)
+  if (newContent === cell.content) {
+    return
   }
+
+  cell.content = newContent
+  schedule(cell.propagators)
 }
diff --git a/src/examples/barometer-belief-system.test.ts b/src/examples/barometer-belief-system.test.ts
index d114167..135531c 100644
--- a/src/examples/barometer-belief-system.test.ts
+++ b/src/examples/barometer-belief-system.test.ts
@@ -417,6 +417,14 @@ test("examples / barometer-belief-system", async () => {
 
   await run()
 
+  log(beliefSystemQuery(buildingHeight.content))
   log(buildingHeight.content)
+  log(beliefSystemQuery(barometerHeight.content))
+
+  // kickOut("pressure")
+
+  // await run()
+
+  // log(beliefSystemQuery(barometerHeight.content))
   // log(beliefSystemQuery(buildingHeight.content))
 })
diff --git a/src/monad/index.ts b/src/monad/index.ts
index 982aedf..4c1fed3 100644
--- a/src/monad/index.ts
+++ b/src/monad/index.ts
@@ -1,4 +1,5 @@
 export * from "./belief-monad.js"
 export * from "./belief-system-monad.js"
+export * from "./merge-conflict-monad.js"
 export * from "./monad.js"
 export * from "./nothing-monad.js"
diff --git a/src/monad/merge-conflict-monad.ts b/src/monad/merge-conflict-monad.ts
new file mode 100644
index 0000000..3f43cef
--- /dev/null
+++ b/src/monad/merge-conflict-monad.ts
@@ -0,0 +1,9 @@
+import { defineHandler } from "../generic/index.js"
+import { isMergeConflict } from "../merge-conflict/index.js"
+import { nothing } from "../nothing/index.js"
+import { isFunction } from "../utils/isFunction.js"
+import { flatten, fmap } from "./monad.js"
+
+defineHandler(fmap, [isFunction, isMergeConflict], (f, ma) => nothing)
+
+defineHandler(flatten, [isMergeConflict], (mma) => nothing)
diff --git a/src/scheduler/run.ts b/src/scheduler/run.ts
index 6a24125..94a6a6a 100644
--- a/src/scheduler/run.ts
+++ b/src/scheduler/run.ts
@@ -1,17 +1,10 @@
 import type { Job } from "./Scheduler.js"
 import { globalScheduler } from "./initializeScheduler.js"
 
-export let isRunning = false
 export async function run(): Promise<void> {
-  try {
-    isRunning = true
-    while (globalScheduler.jobs.length > 0) {
-      // 我们用「先进先出」的方式来处理 job 的 queue。
-      const job = globalScheduler.jobs.shift() as Job
-      await job.propagator()
-    }
-    isRunning = false
-  } catch (error) {
-    console.error({ who: "run", error })
+  while (globalScheduler.jobs.length > 0) {
+    // 我们用「先进先出」的方式来处理 job 的 queue。
+    const job = globalScheduler.jobs.shift() as Job
+    await job.propagator()
   }
 }